PHP: How do I detect if an input string is Arabic

this will check if the string is Arabic Or has Arabic text

text must be UNICODE e.g UTF-8

$str = "بسم الله";
if (preg_match('/[اأإء-ي]/ui', $str)) {
    echo "A match was found.";
} else {
    echo "A match was not found.";
}

Use regular expression for shorter and easy answer

 $is_arabic = preg_match('/\p{Arabic}/u', $text);

This will return true (1) for arabic string and 0 for non arabic string

I would use regular expressions to get the number of Arabic characters and compare it to the total length of the string. If the text is for instance at least 60% Arabic charactes, I would consider it as mainly Arabic and apply RTL formatting.

/**
 * Is the given text mainly Arabic language? 
 *
 * @param string $text string to be tested if it is arabic. :-)
 * @return bool 
 */
function ct_is_arabic_text($text) {
    $text = preg_replace('/[ 0-9\(\)\.\,\-\:\n\r_]/', '', $text); // Remove spaces, numbers, punctuation.
    $total_count = mb_strlen($text); // Length of text
    if ($total_count==0)
        return false;
    $arabic_count = preg_match_all("/[اأإء-ي]/ui", $text, $matches); // Number of Arabic characters
    if(($arabic_count/$total_count) > 0.6) { // >60% Arabic chars, its probably Arabic languages
        return true;
    }
    return false;
}

For inline RTL formatting, use CSS. Example class:

.embed-rtl {
 direction: rtl;
 unicode-bidi: normal;
 text-align: right;
}

public static function isArabic($string){
    if(preg_match('/\p{Arabic}/u', $string))
        return true;
    return false;
}