What is the difference between using str_replace() and strtr() for replacing characters in PHP?

The main difference between str_replace() and strtr() in PHP is that str_replace() replaces all occurrences of a substring within a string, while strtr() replaces specified characters in a string with corresponding values from a translation table. If you need to replace specific characters with specific values, strtr() is more suitable. However, if you simply need to replace all occurrences of a substring with another substring, str_replace() is the better choice.

// Using str_replace() to replace all occurrences of a substring
$string = "Hello, world!";
$new_string = str_replace("world", "PHP", $string);
echo $new_string;

// Using strtr() to replace specified characters with corresponding values
$string = "Hello, world!";
$translation_table = array("H" => "J", "w" => "P");
$new_string = strtr($string, $translation_table);
echo $new_string;