PHP Conditional to see if string contains a variable [duplicate] - php

Question

This question already has answers here:
Problem with Strpos In PHP
(3 answers)
PHP strpos() function returning incorrect result
(1 answer)
Closed 5 years ago.
I'm struggling to figure out how to use PHP strpos to find a variable in a string. The code below works if I enter a number directly but not if I replace the number with a variable I know to be a single number. No PHP errors present but the conditional renders false. I've been searching all over and am stumped by this.
The $string variable returns "253,254,255".
The $current_page_id variable returns "253".
$string = "";
foreach( $page_capabilities as $post):
$string .= $post->ID.',';
endforeach;
if (strpos($string, $current_page_id) !== false) {
// This works
//if (strpos($string, '253') !== false) {
// This does not
if (strpos($string, $current_page_id) !== false) {
echo 'true';
}
}

Answer 1

You don't need that CSV string to check for the ID you're looking for. You can just do it in the foreach loop where you're currently building the string.
foreach ($page_capabilities as $post) {
if ($post->ID == $current_page_id) {
echo 'true';
break; // stop looking if you find it
}
}

Answer 2

You should cast $current_page_id to a string:
if (strpos($string, (string)$current_page_id) !== false) { ...
The following is from php docs:
If needle is not a string, it is converted to an integer and applied
as the ordinal value of a character.
Which means you were comparing "253,254,255" with the character corresponding to 253 in the ASCII table

Answer 3

You need to cast the integer to a string.
$postIDs = [55, 89, 144, 233];
$string = implode(',', $postIDs);
$postID = 55;
if(strpos($string, strval($postID)) !== false) {
echo 'strpos did not return false';
}

Answer 4

I would suggest you to change your approach. You should search for the exact string value. Because as #mickmackusa suggested, it would find 25 & 53 too
$page_capabilities = array(array('POSTID' => 253),array('POSTID' => 254),array('POSTID' => 255));
$current_page_id = '255';
$key = array_search($current_page_id, array_column($page_capabilities, 'POSTID'));
if($key !== false) {
echo 'true';
}