<?php
function substr_count_overlap($string, $needle) {
    $count = 0;
	$start = 0;
	while(1) {
	    $found = strpos($string, $needle, $start);
		if($found !== FALSE) {
		    $count++;
			$start = $found + 1;
	    } else return $count;
	}
	return $count;
}

$myString = 'bababa';
$search = 'baba';

echo substr_count_overlap($myString, $search);

2