Programming

  minte9
LearnRemember



String / Compare

Strict

Not using strict operator === can lead to variable type problems. 
 
$string = "123abc";

echo $string == 123 ? 'true' : 'false'; // true (incorect)
    // "123abc" -> (int) "123abc" -> 123

echo $string === 123 ? 'true' : 'false'; // false (corect)

Safe

Binary safe string comparison. Returns < 0 if str1 is less than str2 Returns > 0 if str1 is greater than str2 Returns 0 if they are equal 
 
echo strcmp("a", "a"); // 0
echo strcasecmp("A", "a"); // 0 (case insensitive)

echo strcmp("A", "a"); // -1
echo strcmp("a", "A"); // 1
Binary safe string comparison (n characters) 
 
$str = "hello John";
echo strncasecmp($str, "Hello World", 5); // 0
substr_compare() 
 
// substr_compare($main_str, $str, $offset, $length, $flag_case)

echo substr_compare("abcde", "bc", 1, 2); // bc, bc = 0
echo substr_compare("abcde", "de", -2, 2); // de, de = 0

echo substr_compare("abcde", "cd", 1, 2); // bc, cd = -1
echo substr_compare("abcde", "bc", 1, 3); // bcd, bc = 1
    // main_str offset is less than str offset

echo substr_compare("abcde", "BC", 1, 2, true); // bc, bc = 0
    // Third parameter - case insenstivity
    
echo substr_compare("abcde", "abc", 5, 1); // Warning
    // Offset is equal or greater than string legth

Similar

similar_text() returns the number of matching chars in both strings. 
 
echo similar_text("cat", "can"); // 2

similar_text("cat", "can", $percent);
echo $percent; // 66,6

Levenshtein

Minimal number of characters you have to replace. Insert or delete to transform str1 into str2. 
 
echo levenshtein('cat', 'can'); // 1

Soundex

Words pronounced similarly produce the same soundex key. Can be used to simplify searches in databases. 
 
echo soundex('wise'); // W200
echo soundex('ways'); // W200

Metaphone

More precise than soundex. It is based in english pronunciation rules - limited global use. 
 
echo soundex('programming') == soundex('programmer'); // TRUE
    // P626 == P626

echo metaphone('programming') != metaphone('programmer'); // TRUE
    // PRKRMNK != PRKRMR




References