100 PHP Functions You Should Know – Part 1

In this tutorial we will discover the list of the 100 most used native functions in PHP.

1. count

Returns the number of elements in an array.


<?php
    $colors=array("Blue","Orange","red");
    echo count($colors);
?>

<?php

$colors=array("Blue","Orange","red");

echo count($colors);

Output:

3

2. is_array

Is used to determine whether a variable is an array or not.


<?php
    $tab = array('X','Y','X');
    if (is_array($tab))
        echo "This is an array....";
    else
        echo "This is not a table....";
?>

<?php

$tab = array('X','Y','X');

if (is_array($tab))

echo "This is an array....";

else

echo "This is not a table....";

Output:


This is an array....

This is an array....

3. substr

Returns part of a string.


<?php
       echo substr("Welcom to Code4Example", 10);
?>

<?php

echo substr("Welcom to Code4Example", 10);

Output:


Code4Example

Code4Example

4. in_array

Finds a specific value in an array.


<?php
    $colors = array("Blue", "Orange", "Red");
    if (in_array("Red", $colors)) {
        echo "Red was found";
    }
    if (in_array("Green", $colors)) {
        echo "Green was found";
    }
?>

<?php

$colors = array("Blue", "Orange", "Red");

if (in_array("Red", $colors)) {

echo "Red was found";

}

if (in_array("Green", $colors)) {

echo "Green was found";

}

Output:


Red was found

Red was found

5. explode

Divide a string into an array.


<?php
    $str = "Welcom to Code4Example";
    print_r (explode(" ",$str));
?>

<?php

$str = "Welcom to Code4Example";

print_r (explode(" ",$str));

Output:


Array
(
    [0] => Welcom
    [1] => to
    [2] => Code4Example
)

Array

(

[0] => Welcom

[1] => to

[2] => Code4Example

)

6. implode

Returns a string from the elements of an array.


<?php
     $arr = array('Hello', 'World!', 'How', 'are', 'you?');
     echo implode(" ",$arr);
?>

<?php

$arr = array('Hello', 'World!', 'How', 'are', 'you?');

echo implode(" ",$arr);

Output:


Hello World! How are you?

Hello World! How are you?

7. str_replace

Divide a string into an array.


<?php
    echo str_replace("Welcom", "Hello", "Welcom to Code4Example!");
?>

<?php

echo str_replace("Welcom", "Hello", "Welcom to Code4Example!");

Output:


Hello to Code4Example!

Hello to Code4Example!

8. strlen

Returns the length of a string.


<?php
    echo strlen("Code4Example");
?>

<?php

echo strlen("Code4Example");

Output:

12

9. array_merge

Merges one or more tables into a single table.


<?php
     $c1=array("blue","orange");
     $c2=array("green","red");
     print_r(array_merge($c1,$c2));
?>

<?php

$c1=array("blue","orange");

$c2=array("green","red");

print_r(array_merge($c1,$c2));

Output:


Array
(
    [0] => blue
    [1] => orange
    [2] => green
    [3] => red
)

Array

(

[0] => blue

[1] => orange

[2] => green

[3] => red

)

10. strpos

Finds the position of the first occurrence of one string within another string.


<?php
    echo strpos("I love english, I love english too!","english");
?>

<?php

echo strpos("I love english, I love english too!","english");

Output:

7

11. preg_match

Finds the pattern in a string, returning true if the pattern exists, otherwise false.


<?php
    preg_match("/^sad/", "Alex was sad");       // returns false
    preg_match("/^sad/", "sad Alex!");         // returns true
?>

<?php

preg_match("/^sad/", "Alex was sad"); // returns false

preg_match("/^sad/", "sad Alex!"); // returns true

12. sprintf

Creates a formatted string from one or more arguments.


<?php
    $str = "Welcom";
    $n = 2;
    $formatted_str = sprintf('%s, to %uth chapter of PHP.',$str, $n);
    echo $formatted_str;
?>

<?php

$str = "Welcom";

$n = 2;

$formatted_str = sprintf('%s, to %uth chapter of PHP.',$str, $n);

echo $formatted_str;

Output:


Welcom, to 2th chapter of PHP.

Welcom, to 2th chapter of PHP.

13. trim

Removes spaces and other predefined characters from both sides of a string.


<?php
     $str = '      Welcome to code4example.com     ';
     $res = trim($str);
     echo $res;
?>

<?php

$str = ' Welcome to code4example.com ';

$res = trim($str);

echo $res;

Output:


Welcome to code4example.com

Welcome to code4example.com

14. strtolower

Converts a string to lowercase.


<?php
     echo strtolower("Hello WORLD.");
?>

<?php

echo strtolower("Hello WORLD.");

Output:


hello world.

hello world.

15. file_exists

Checks whether a file or directory exists or not.


<?php
     echo file_exists("file.txt");
?>

<?php

echo file_exists("file.txt");

16. is_string

Is used to determine whether a variable is a string or not.


<?php
   if (is_string("0011"))
        echo "It's a string\n";
   else
       echo "It is not a string";
?>

<?php

if (is_string("0011"))

echo "It's a string\n";

else

echo "It is not a string";

Output:


It's a string

It's a string

17. preg_replace

To perform a pattern match on a string, then replace the match with specific text. This example removes spaces in $str.


<?php
    $str = 'Hello        sir';
    $str = preg_replace('/\s\s+/', ' ', $str);
    echo $str;
?>

<?php

$str = 'Hello sir';

$str = preg_replace('/\s\s+/', ' ', $str);

echo $str;

Output:


Hello sir

Hello sir

18. file_get_contents

Read a file in a character string.


<?php
      echo file_get_contents("file.txt");
?>

<?php

echo file_get_contents("file.txt");

19. array_key_exists

Checks an array for a specified key and returns true if the key exists and false if the key does not exist.


<?php
   $car = array("Renault"=>"Kangoo", "Peugeot"=>"Crossover");
   if (array_key_exists("Renault",$car))
   {
        echo "The key exists!";
   }
   else
   {
        echo "The key does not exist!";
  }
?>

<?php

$car = array("Renault"=>"Kangoo", "Peugeot"=>"Crossover");

if (array_key_exists("Renault",$car))

{

echo "The key exists!";

}

else

{

echo "The key does not exist!";

}

Output:


The key exists!

The key exists!

20. array_keys

Returns an array containing the keys.


<?php
    $car  = array("Renault"=>"Kangoo", "Peugeot"=>"Crossover", "Toyota"=>"4X4");
    print_r(array_keys($car));
?>

<?php

$car = array("Renault"=>"Kangoo", "Peugeot"=>"Crossover", "Toyota"=>"4X4");

print_r(array_keys($car));

Output:


Array
(
    [0] => Renault
    [1] => Peugeot
    [2] => Toyota
)

Array

(

[0] => Renault

[1] => Peugeot

[2] => Toyota

)

21. dirname

Returns the name of the directory for a given path.


<?php
     echo dirname("/path/script.php");
?>

<?php

echo dirname("/path/script.php");

22. function_exists

Check if a function exists or not in the PHP script.


<?php
   function displayMsg()
   {
        echo "Welcome to Code4Example";
   }
  
   // Checks if the function named displayMsg exists or not
   if (function_exists ('displayMsg'))
   {
        echo "The displayMsg () function exists.\n";
   }
   else
   {
        echo "The displayMsg () function does not exist.\n";
   }
?>

<?php

function displayMsg()

{

echo "Welcome to Code4Example";

}

// Checks if the function named displayMsg exists or not

if (function_exists ('displayMsg'))

{

echo "The displayMsg () function exists.\n";

}

else

{

echo "The displayMsg () function does not exist.\n";

}

Output:


The displayMsg () function exists.

The displayMsg () function exists.

23. array_map

Sends each value of an array to a user-defined function and returns an array with the new values, provided by the user-defined function.


<?php
   function multiplication($n)
   {
     return($n * $n);
   }

   $tab = array(1,2,3,4);
   print_r(array_map("multiplication", $tab));
?>

<?php

function multiplication($n)

{

return($n * $n);

}

$tab = array(1,2,3,4);

print_r(array_map("multiplication", $tab));

Output:


Array
(
    [0] => 1
    [1] => 4
    [2] => 9
    [3] => 16
)

Array

(

[0] => 1

[1] => 4

[2] => 9

[3] => 16

)

24. get_class

This function retrieves the class name of the given object.


<?php
   // create an object
   $obj = new Foo();
   // get the class name
   echo get_class($obj);
?>

<?php

// create an object

$obj = new Foo();

// get the class name

echo get_class($obj);

25. class_exists

This function checks if the given class has been defined.


<?php
   if (class_exists('Foo')) {
         $obj = new Foo();
   }
?>

<?php

if (class_exists('Foo')) {

$obj = new Foo();

}

26. is_object

Is used to determine whether a variable is an object or not.


<?php
    if (!is_object($obj)) {
        return false;
    }
?>

<?php

if (!is_object($obj)) {

return false;

}

27. time

Function returns the current time as seconds.


<?php
    $t = time();
    echo($t);
?>

<?php

$t = time();

echo($t);

28. json_encode

Function that converts PHP objects to JSON.


<?php
$obj->nom = "Alex";
$obj->age = 24;

$json = json_encode($obj);

echo $json;
?>

<?php

$obj->nom = "Alex";

$obj->age = 24;

$json = json_encode($obj);

echo $json;

29. date

This function allows you to format a date.


<?php
      echo "Today it's ". date("Y/m/d");
      echo "Today it's ". date("Y.m.d");
      echo "Today it's ". date("Y-m-d");
?>

<?php

echo "Today it's ". date("Y/m/d");

echo "Today it's ". date("Y.m.d");

echo "Today it's ". date("Y-m-d");

30. is_null

Function is used to test whether a variable is NULL or not.


<?php
     $var = TRUE;
     if (is_null($var))
     {
           echo "The variable is NULL";
     }
     else
     {
           echo "The variable is not NULL";
     }
?>

<?php

$var = TRUE;

if (is_null($var))

{

echo "The variable is NULL";

}

else

{

echo "The variable is not NULL";

}

31. is_numeric

Is used to check whether a variable is numeric or not.


<?php
  $var = 678;

  if (is_numeric($var))
  {
    echo "$var is a numeric value." ;
  }
  else
  {
    echo "$var is not a numeric value." ;
  }
?>

<?php

$var = 678;

if (is_numeric($var))

{

echo "$var is a numeric value." ;

}

else

{

echo "$var is not a numeric value." ;

}

Output:


678 is a numeric value.

678 is a numeric value.

32. array_shift

Removes the first element from an array and returns the value of the deleted element.


<?php
   $colors = array(0=>"orange",  1=>"green",  2=>"blue");
   echo array_shift($colors);
   print_r ($colors);
?>

<?php

$colors = array(0=>"orange", 1=>"green", 2=>"blue");

echo array_shift($colors);

print_r ($colors);

33. defined

Checks if a constant exists.


<?php
     define("PI", 3.14);
     echo defined("PI");
?>

<?php

define("PI", 3.14);

echo defined("PI");

34. is_dir

Checks whether the specified file is a directory.


<?php
  $directory = "documents";
  if(is_dir($directory))
  {
      echo ("$directory is a directory");
  }
  else
  {
      echo ("$directory is not a directory");
  }
?>

<?php

$directory = "documents";

if(is_dir($directory))

{

echo ("$directory is a directory");

}

else

{

echo ("$directory is not a directory");

}

35. json_decode

Decode a JSON string


<?php
    $json = '{"a":1,"b":2,"c":3}';
    var_dump(json_decode($json));
?>

<?php

$json = '{"a":1,"b":2,"c":3}';

var_dump(json_decode($json));

36. header

Sends a raw HTTP header to a client.


<?php
header("Expires: Tur, 11 May 2022 01:00:00 GMT");
header("Pragma: no-cache");
header("Cache-Control: no-cache");
?>

<?php

header("Expires: Tur, 11 May 2022 01:00:00 GMT");

header("Pragma: no-cache");

header("Cache-Control: no-cache");

37. strtoupper

Converts a string to uppercase.


<?php
      echo strtoupper("Hello WORLD!");
?>

<?php

echo strtoupper("Hello WORLD!");

38. array_values

Returns an array containing all the values of an array.


<?php
  $info = array("Name"=>"Peter", "Age"=>"26", "City"=>"L.A.");
  print_r(array_values($info));
?>

<?php

$info = array("Name"=>"Peter", "Age"=>"26", "City"=>"L.A.");

print_r(array_values($info));

Output:


Array
(
    [0] => Peter
    [1] => 26
    [2] => L.A.
)

Array

(

[0] => Peter

[1] => 26

[2] => L.A.

)

39. md5

Calculates the MD5 hash of a string.


<?php
     $str = "Code4Example";
     echo md5($str);
?>

<?php

$str = "Code4Example";

echo md5($str);

40. method_exists

It checks if the “write” method exists in the object supplied as the “$book” parameter.


<?php
   $book = new Book();
   var_dump(method_exists($book, 'write'));
?>

<?php

$book = new Book();

var_dump(method_exists($book, 'write'));

41. file_put_contents

Write the string of characters “Welcom to Code4Exampe! “In the file” file.txt.


<?php
  echo file_put_contents("file.txt","Welcom to Code4Example!");
?>

<?php

echo file_put_contents("file.txt","Welcom to Code4Example!");

42. rtrim

Removes spaces or other predefined characters to the right of a string.


<?php
  $var = "Hello Code4Example!";
  echo rtrim($var, "Code4Example!");
?>

<?php

$var = "Hello Code4Example!";

echo rtrim($var, "Code4Example!");

43. array_pop

Remove the last element from an array.


<?php
    $colors = array("orange","yellow","blue");
    array_pop($colors);
    print_r($colors);
?>

<?php

$colors = array("orange","yellow","blue");

array_pop($colors);

print_r($colors);

44. unlink

Delete a file.


<?php
  $file = "file.txt";
  if (!unlink($file))
  {
      echo ("Error during deletion");
  }
  else
  {
      echo ("File deleted");
  }
?>

<?php

$file = "file.txt";

if (!unlink($file))

{

echo ("Error during deletion");

}

else

{

echo ("File deleted");

}

45. basename

Returns the file name from a path.


<?php
     $path = "/prog/app.php";
     echo basename($path);
?>

<?php

$path = "/prog/app.php";

echo basename($path);

46. realpath

Returns the absolute path.


<?php
      echo realpath("myfile.txt");
?>

<?php

echo realpath("myfile.txt");

47. call_user_func

Is used to call a callback function given in the first parameter and passes the remaining parameters as arguments. It is used to call user-defined functions.


<?php
  function display($val) 
  { 
      echo "This is the $value site.\n"; 
  } 

  call_user_func('display', "Code4Example.com"); 
?>

<?php

function display($val)

{

echo "This is the $value site.\n";

}

call_user_func('display', "Code4Example.com");

48. call_user_func_array

Calls a callback function and passes the parameters to it. The parameters are encapsulated in an array and then assigned one by one to the callback function parameter list. You call the callback function by the fully qualified name assigned to it in the first parameter. If the callback function returns a value, that value is returned by call_user_func_array.


<?php
     $mult = function($nbr1, $nbr2) {
         return $nbr1 * $nbr2;
     };

     var_dump(call_user_func_array($mult, array(3, 2)));
?>

<?php

$mult = function($nbr1, $nbr2) {

return $nbr1 * $nbr2;

};

var_dump(call_user_func_array($mult, array(3, 2)));

49. fopen

Open a file or URL.


<?php
    $file = fopen("myFile.txt","r");
    $url = fopen("http://code4example.com/","r"); 
?>

<?php

$file = fopen("myFile.txt","r");

$url = fopen("http://code4example.com/","r");

50. microtime

Returns the current Unix timestamp in microseconds.


<?php
     echo(microtime());
?>

<?php

echo(microtime());

The 100 PHP Functions You Should Know – Part 2

1 Comment

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1. count

2. is_array

3. substr

4. in_array

5. explode

6. implode

7. str_replace

8. strlen

9. array_merge

10. strpos

11. preg_match

12. sprintf

13. trim

14. strtolower

15. file_exists

16. is_string

17. preg_replace

18. file_get_contents

19. array_key_exists

20. array_keys

21. dirname

22. function_exists

23. array_map

24. get_class

25. class_exists

26. is_object

27. time

28. json_encode

29. date

30. is_null

31. is_numeric

32. array_shift

33. defined

34. is_dir

35. json_decode

36. header

37. strtoupper

38. array_values

39. md5

40. method_exists

41. file_put_contents

42. rtrim

43. array_pop

44. unlink

45. basename

46. realpath

47. call_user_func

48. call_user_func_array

49. fopen

50. microtime

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