PHP already have the function that check if a substring exists in another string. It's called strpos().
This function returns the position of substring when the substring is
found and return false otherwise. Using the example string you gave me
the code will look like this :
$string = "walawalabingbang";
$substring = "bing";
if (strpos($string, $substring) !== false) {
// Yes, '$substring' is found in '$string';
// ... do whatever you wish down here
} else {
// Nope, can't find '$substring' in '$string';
// ... do something here?
}
Please remember that when you're using strpos() always use the === or !== operator to test for equality / inequality instead of == or !=. Here's the reason. If you're testing the existence of "wala" in the string then the result of strpos("walawalabingbang", "wala") is zero. Since php treat zero as false the result of strpos("walawalabingbang", "wala") != false is false so even though the substring is found right there at the beginning you would end up going to the else block