How to use strpos to determine if a string exists in input string?

Question

$filename = \'my_upgrade(1).zip\';
$match = \'my_upgrade\';

if(!strpos($filename, $match))
    {
    die();
    }
else 
   {
   //proceed
   }

In

Answer 1

The strpos() function is case-sensitive.

if(strpos($filename, $match) !== false)
        {
        // $match is present in $filename
        }
    else 
       {
       // $match is not present in $filename 
       }

For using case-insensitive. use stripos() that is it finds the position of the first occurrence of a string inside another string (case-insensitive)

Answer 2

$data = 'match';
$line = 'match word in this line';
if(strpos($line,$data) !== false){
    echo "data found";
}else{
    echo "no data found";
}

Answer 3

strpos in this case will return a zero, which is then interpretted as false when you do the logical negation. You should check explicitly for the boolean false.

Answer 4

strpos returns false if the string is not found, and 0 if it is found at the beginning. Use the identity operator to distinguish the two:

if (strpos($filename, $match) === false) {

By the way, this fact is documented with a red background and an exclamation mark in the official documentation.

Answer 5

if (strpos($filename, $match) === false)

Otherwise, strpos will return 0 (the index of the match), which is false.

The === operator will also compare type of the variables (boolean != integer)

Answer 6

This working for me when everything other fail in some situations:

$filename = 'my_upgrade(1).zip';
$match = 'my_upgrade';
$checker == false;
if(strpos($filename, $match))
    {
    $checker == true;
    }
if ($checker === false)
{ 
die();
}
else 
{
//proceed
}

Or in short:

$filename = 'my_upgrade(1).zip';
$match = 'my_upgrade';
$checker == false;
if(strpos($filename, $match))
    {
    $checker == true;
//proceed
 }
if ($checker === false)
{ 
die();
}