strpos
strpos() is a built-in PHP function that finds the position of the first occurrence of a string inside another string.
It is often used to check if a string contains another string. When the presence of the string is the main goal of the check, it is advantageously replaced by str_contains(), str_starts_with() or str_ends_with(). Otherwise, this function is prone to the strpos() syndrome, a classic PHP trap.
strpos() has a case-insensitive version called stripos().
<?php
if(strpos('abc', 'b')) {
print "The string contains a `b`.";
}
// Error! 'a' is at position 0, which is confused with false
if(strpos('abc', 'a')) {
print "The string contains a `b`.";
}
// This is OK
if(strpos('abc', 'a') !== false) {
print "The string contains a `b`.";
}
?>