简单的strpos（）无法与“ [”字符一起使用，为什么？

Question

why does if i do:

if(strpos("[","[rgeger]")){ 
echo 'hey'; 
}

it doesn't prints anything?

try this with a string:

function return_tags($keywords){
 if($keywords){
  $k_array = array();

  foreach($this->check($keywords) as $key=>$value){

    array_push($k_array, $value);
  }

  $last_array = array();
  foreach($k_array as $key=>$value){
    if(strpos("[", $value) && strpos("]", $value) && strlen($value) >= 2){
      $value = '<span class="tag">'.$value.'</span>';

    }
    array_push($last_array, trim($value));

  }
  return $last_array;

 }else{
  return false;
 }
}

string example

  $keywords = "freignferi eiejrngirj erjgnrit [llll] [print me as tag]";

did you see any <span> element printed in html?

Answer 1

It looks like you swapped the arguments:

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

So if you want to know if a [ is in your string [rgeger] :

if (strpos("[rgeger]", "[") !== false) { 
  echo 'hey'; 
}

(Source: http://php.net/strpos )

Answer 2

The position returned is zero-indexed, so the first character is at position 0. When evaluating 0 as Boolean, it's false - so it doesn't get into the block.

Fix with this:

if (strpos('[rgeger]', '[') !== false)

Also the arguments are the wrong way round. Don't upvote this post any more; go upvote robbi's instead for spotting that one :) Eagle eyes robbi, EAGLE eyes :P

Answer 3

Because you have to check the return value of strpos() as it could be zero because [ it's at index zero, and zero evaluates to FALSE that's why it wouldn't enter your if block, so check that the return value it's FALSE and type boolean, not just integer zero, like this:

if(strpos("[rgeger]","[") !== false){ 
  echo 'hey'; 
}

UPDATE:
The parameters were in wrong order too, the subject string comes first then the search string, I updated my code above to reflect that.

Answer 4

Because its wrong. Strpos give false if the condition is false.

if(strpos("[rgeger]","[") !== false){ 
    echo 'hey'; 
}

Edit: I have corrected my answer. Your parameter are in the wrong order. Its:

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

Answer 5

Because actually strpos can return 0 see doc .

Warning This function may return Boolean FALSE, but may also return a non-Boolean value which evaluates to FALSE. Please read the section on Booleans for more information. Use the === operator for testing the return value of this function.

So you have to compare with the false value directly.

if(strpos("[","[rgeger]") !== false){ 
  echo 'hey'; 
}

EDIT ::

Careful.. Look at the arguments order

int strpos ( string $haystack , mixed $needle [, int $offset = 0 ] )

Haystack is the string input. Needle is what you are seeking for.

if(strpos("[regeger]","[") !== false){ 
  echo 'hey'; 
}