How to check if a string is in an array?

I basically need a function to check whether a string's characters (each character) is in an array.

My code isn't working so far, but here it is anyway,

$allowedChars = array("a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"," ","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"," ","0","1","2","3","4","5","6","7","8","9"," ","@",".","-","_","+"," ");

$input = "Test";
$input = str_split($input);

if (in_array($input,$allowedChars)) {echo "Yep, found.";}else {echo "Sigh, not found...";}

I want it to say 'Yep, found.' if one of the letters in $input is found in $allowedChars. Simple enough, right? Well, that doesn't work, and I haven't found a function that will search a string's individual characters for a value in an array.

By the way, I want it to be just those array's values, I'm not looking for fancy html_strip_entities or whatever it is, I want to use that exact array for the allowed c开发者_如何学Goharacters.

You really should look into regex and the preg_match function: http://php.net/manual/en/function.preg-match.php

But, this should make your specific request work:

$allowedChars = array("a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"," ","A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R","S","T","U","V","W","X","Y","Z"," ","0","1","2","3","4","5","6","7","8","9"," ","@",".","-","_","+"," ");
$input = "Test";
$input = str_split($input);
$message = "Sigh, not found...";
foreach($input as $letter) {
    if (in_array($letter, $allowedChars)) {
        $message = "Yep, found.";
        break;
    }
}
echo $message;

Are you familiar with regular expressions at all? It's sort of the more accepted way of doing what you're trying to do, unless I'm missing something here.

Take a look at preg_match(): http://php.net/manual/en/function.preg-match.php

To address your example, here's some sample code (UPDATED TO ADDRESS ISSUES IN COMMENTS):

$subject = "Hello, this is a string";
$pattern = '/[a-zA-Z0-9 @._+-]*/'; // include all the symbols you want to match here

if (preg_match($pattern, $subject))
    echo "Yep, matches";
else
    echo "Doesn't match :(";

A little explanation of the regex: the '^' matches the beginning of the string, the '[a-zA-Z0-9 @._+-]' part means "any character in this set", the '*' after it means "zero or more of the last thing", and finally the '$' at the end matches the end of the string.

A somewhat different approach:

$allowedChars = array("a","b","c","d","e");
$char_buff = explode('', "Test");
$foundTheseOnes = array_intersect($char_buff, $allowedChars);
if(!empty($foundTheseOnes)) {
    echo 'Yep, something was found. Let\'s find out what: <br />';
    print_r($foundTheseOnes);
}

Validating the characters in a string is most appropriately done with string functions.
preg_match() is the most direct/elegant method for this task.

Code: (Demo)

$input="Test Test Test Test";
if(preg_match('/^[\w +.@_-]*$/',$input)){
    echo "Input string does not contain any disallowed characters";
}else{
    echo "Input contains one or more disallowed characters";
}
// output: Yes, input contains only allowed characters

Pattern Explanation:

/          # start pattern
^          # start matching from start of string
[\w +.@-]  # match: a-z, A-Z, 0-9, underscore, space, plus, dot, atsign, hyphen
*          # zero or more occurrences
$          # match until end of string
/          # end pattern

Significant points:

• The ^ and $ anchors are crucial to ensure that the entire string is validated versus just a substring of the string.
• The \w (a.k.a. "any word character" -> a shorthand character class) is the easy way to write: [a-zA-Z0-9_]
• The . dot character loses its "match anything (almost)" meaning and becomes literal when it is written inside of a character class. No escaping slash is necessary.
• The hyphen inside of a character class can be written without an escaping slash (\-) so long as the it is positioned at the start or end of the character class. If the hyphen is not at the start/end and it is not escaped, it will create a range of characters between the characters on either side of it.
  Like it or not, [.-z] will not match a hyphen symbol because it does not exist "between" the dot character and the lowercase letter z on the ascii table.
• The * that follows the character class is the "quantifier". The asterisk means "0 or more" of the preceding character class. In this case, this means that preg_match() will allow an empty string. If you want to deny an empty string, you can use + which means "1 or more" of the preceding character class. Finally, you can be far more specific about string length by using a number or numbers in a curly bracketed expression.
  • {8} would mean the string must be exactly 8 characters long.
  • {4,} would mean the string must be at least 4 characters long.
  • {,10} would mean the string length must be between 0 and 10.
  • {5,9} would mean the string length must be between 5 and 9 characters.

All of that advice aside, if you absolutely must use your array of characters AND you wanted to use a loop to check individual characters against your validation array (and I certainly don't recommend it), then the goal should be to reduce the number of array elements involved so as to reduce total iterations.

• Your $allowedChars array has multiple elements that contain the space character, but only one is necessary. You should prepare the array using array_unique() or a similar technique.
• str_split($input) will run the chance of generating an array with duplicate elements. For example, if $input="Test Test Test Test"; then the resultant array from str_split() will have 19 elements, 14 of which will require redundant validation checks.
• You could probably eliminate redundancies from str_split() by calling count_chars($input,3) and feeding that to str_split() or alternatively you could call str_split() then array_unique() before performing the iterative process.

Because you're just validating a string, see preg_match() and other PCRE functions for handling this instead.

Alternatively, you can use strcspn() to do...

$check = "abcde.... '; // fill in the rest of the characters
$test = "Test";
echo ((strcspn($test, $check) === strlen($test)) ? "Sigh, not found..." : 'Yep, found.');