字符串搜索中的 strpos 和字符串

Question

I have a comma delimited string and I need to be able to search the string for instances of a given string. I use the following function:

function isChecked($haystack, $needle) {
    $pos = strpos($haystack, $needle);
    if ($pos === false) {
        return null;
    } else {
        'return 'checked="checked"';
    }
}

Example: isChecked('1,2,3,4', '2') searches if 2 is in the string and ticks the appropriate checkbox in one of my forms.

When it comes to isChecked('1,3,4,12', '2') though, instead of returning NULL it returns TRUE , as it obviously finds the character 2 within 12 .

How should I use the strpos function in order to have only the correct results?

Answer 1

function isChecked($haystack, $needle) {
    $haystack = explode(',', $haystack);
    return in_array($needle, $haystack);
}

Also you can use regular expressions

Answer 2

Using explode() might be the best option, but here's an alternative:

$pos = strpos(','.$haystack.',', ','.$needle.','); 

Answer 3

Simplest way to do it may be splitting $haystack into array and compare each element of array with $needle .

Things used [except used by you like if and function]: explode() foreach strcmp trim

Funcion:

function isInStack($haystack, $needle) 
{
    # Explode comma separated haystack
    $stack = explode(',', $haystack);

    # Loop each
    foreach($stack as $single)
    {
          # If this element is equal to $needle, $haystack contains $needle
          # You can also use strcmp:
          # if( strcmp(trim($single), $needle) )
          if(trim($single) == $needle)
            return "Founded = true";        
    }
    # If not found, return false
    return null;
}

Example:

var_dump(isInStack('14,44,56', '56'));

Returns:

 bool(true)

Example 2:

 var_dump(isInStack('14,44,56', '5'));

Returns:

 bool(false)

Hope it helps.

Answer 4

function isChecked($haystack, $needle) 
{
    $pos = strpos($haystack, $needle);
    if ($pos === false)
    {
        return false;
    } 
    else 
    {
        return true;
    }
}