PHP | preg_grep() Function

Last Updated : 11 Jul, 2025

The preg_grep() is an inbuilt function in PHP. It returns the array consisting of the elements of the input array that match with the given pattern. Syntax :

array preg_grep ( $pattern, $input [, $flags] )

Parameters Used: The preg_grep() function take three parameters that are described below:

$pattern: The $pattern is an string element which is searched in string array.
$input: The $input is the original string array.
$flags: The $flags is used for signalize and its variable type used for indicates two states True or False to control the program. If the flag is set to PREG_GREP_INVERT, the function returns elements of the input array that do not match to the given pattern.

Return Values: The function returns array indexed using the keys from the input array. Program 1:

php

<?php
// PHP program to implement
// preg_grep() function

// original array elements 
$inputstrVal =array("Geeks", "for", "Geeks", '2018'    );

// Search elements "o", followed by one 
// or more letters.
$result=preg_grep ('/o(\w+)/', $inputstrVal );

print_r($result);
?>

Output:

Array
(
    [1] => for
)

Program 2: Take an example of PREG_GREP_INVERT, which is invert data instead of output numbers to be non-numeric values in php.

php

<?php
// PHP program to implement preg_grep()
// function input string
$inputstrVal= array(1, "one", 2, "two",
              "three", 4, 5, "Six", 7,
              "Eight", "Nine", 10,
               11, 12, 13);
// Used preg_grep with PREG_GREP_INVERT           
$result = preg_grep("/[0-9]/",  $inputstrVal,
                            PREG_GREP_INVERT);
// Print result     
print_r($result);
?>

Output:

Array
(
    [1] => one
    [3] => two
    [4] => three
    [7] => Six
    [9] => Eight
    [10] => Nine
)

Program 3: Example where no match found, then it return NULL array.

php

<?php
// PHP program to implement
// preg_grep() function

//original array elements 
 $inputstrVal =array(0 =>"Geeks", 
                    1 =>"for", 
                    2 => "Geeks",
                    3 => '2018',
                    
                );
// Search elements "x", followed by one 
// or more letters.
$result=preg_grep ('/x(\w+)/', $inputstrVal );

print_r($result);
?>