How to Check if a String Contains a Substring in PHP

1. Use the strpos() Function to Check if a String Contains a Substring in PHP
2. Use the preg_match() Function to Check if a String Contains a Substring in PHP

This article will introduce different methods to check if a string contains a substring in PHP using the strpos() and preg_match() functions.

Use the strpos() Function to Check if a String Contains a Substring in PHP

We will use the built-in function strpos() to check if a string contains a substring. This command checks the occurrence of a passed substring; the correct syntax to execute this is as follows:

strpos($originalString, $checkString, $offset);

The built-in function strpos() has three parameters, which are discussed below:

This function returns the position of the substring relative to the position of the original string. The program below shows how we can use the strpos() function to check if a string contains a substring.

<?php
$mystring = "This is a PHP program.";

if (strpos($mystring, "program.") !== false) {
    echo("True");
}
?>

Output:

True

If we pass the $offset parameter, the function will start the search from the specified location.

<?php
$mystring = "This is a PHP program.";

if (strpos($mystring, "PHP", 13) !== false) {
    echo("True");
} else {
    echo("False");
}
?>

Output:

False

The output has shown False because the string that we searched was before the offset.

Use the preg_match() Function to Check if a String Contains a Substring in PHP

In PHP, we can also use the preg_match() function to check if a string contains a specific word. This function uses regular expressions to match patterns. The correct syntax to use this function is as follows:

preg_match($pattern, $inputString, $matches, $flag, $offset);

The function preg_match() accepts five parameters. The detail of its parameters is as follows

We will use the pattern /{$search}/i to check for a specific word. The program that checks if a string contains a specific word is as follows:

<?php
$mystring = "This is a php program.";
$search = "a";
if(preg_match("/{$search}/i", $mystring)) {
    echo "True"; } else {
    echo("False");
}
?>

Output:

True