Find multiple string positions in PHP

Question

I`m writing a PHP page that parses given URL. What I can do is find the first occurrence only, yet when I echo it, I get another value rather than the given.

this is what I did till now.

<?php
$URL = @"my URL goes here";//get from database
$str = file_get_contents($URL);
$toFind = "string to find";
$pos = strpos(htmlspecialchars($str),$toFind);
echo substr($str,$pos,strlen($toFind)) . "<br />";
$offset = $offset + strlen($toFind);
?>

I know that a loop can be used, yet I don`t know the condition neither the body of the loop would be.

And how can I show the output I need??

Answer 1

This happens because you are using strpos on the htmlspecialchars($str) but you are using substr on $str.

htmlspecialchars() converts special characters to HTML entities. Take a small example:

// search 'foo' in '&foobar'

$str = "&foobar";
$toFind = "foo";

// htmlspecialchars($str) gives you "&foobar"
// as & is replaced by &. strpos returns 5
$pos = strpos(htmlspecialchars($str),$toFind);

// now your try and extract 3 char starting at index 5!!! in the original
// string even though its 'foo' starts at index 1.
echo substr($str,$pos,strlen($toFind)); // prints ar

To fix this use the same haystack in both the functions.

To answer you other question of finding all the occurrences of one string in other, you can make use of the 3rd argument of strpos, offset, which specifies where to search from. Example:

$str = "&foobar&foobaz";
$toFind = "foo";
$start = 0;
while(($pos = strpos(($str),$toFind,$start)) !== false) {
        echo 'Found '.$toFind.' at position '.$pos."\n";
        $start = $pos+1; // start searching from next position.
}

Output:

Found foo at position 1
Found foo at position 8

Answer 2

Use:

while( ($pos = strpos(($str),$toFind,$start)) != false) {  

Explenation: Set ) after false behind $start), so that $pos = strpos(($str),$toFind,$start) is placed between ().

Also use != false, because php.net says: 'This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE, such as 0 or "". Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.