Help with loop

[kdlklm]

I can't seem to figure out why this will not work.

 $instance = 1;  

for ($i=0; $i<=strlen($olmp_content); $i++) {  

    if (substr($olmp_content, $i, 4) == "<tr class=\"one\">") {  

        if ($instance % 2 == 0) {  

            $olmp_content= substr_replace($olmp_content, "<tr class=\"Body2\">", $i, 4); 
        }  

        $instance++;  

    }  

} 
unset ($instance, $i);

[kdlklm]

I got it

 $instance = 1;  

for ($i=0; $i<=strlen($olmp_content); $i++) {  

    if (substr($olmp_content, $i, 16) == "<tr class=\"one\">") {  

        if ($instance % 2 == 0) {  

            $olmp_content= substr_replace($olmp_content, "<tr class=\"Body2\">", $i, 16); 
        }  

        $instance++;  

    }  

} 
unset ($instance, $i);