Experienced PHP Questions and Answers

Question: Difference between array_map, array_walk and array_filter?
array_map: This function applies the callback to the elements of the given arrays.

$arrayData= array_map('strtolower', array('One','Two','three'));
print_r($arrayData); //array ( [0] => one [1] => two [2] => three )

array_walk: This function apply a user supplied function to every member of an array

function my_function(&$item, $key){
array_walk($arrayData, 'my_function');
print_r($arrayData); //Array ( [0] => One1 [1] => Two2 [2] => three3 )

array_filter: This function filters elements of an array using a callback function.

function odd_number($item){
    return false;
    return true;
$arrayData=array_filter($arrayData, 'odd_number');
print_r($arrayData); //Array ( [0] => 1 [2] => 3 [4] => 5 )

Question: How to convert date to timestamp in PHP??

echo strtotime('2015-09-15'); //1442275200

Question: Give an easy way to encrypt/decrypt the password?

define('SALT', 'X4DSF464ADS6SC5C5D55D5'); 
function encrypt_string($text) 
    return trim(base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, SALT, $text, MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND)))); 

function decrypt_string($text) 
    return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, SALT, base64_decode($text), MCRYPT_MODE_ECB, mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB), MCRYPT_RAND))); 

echo $msg = encrypt_string("your message"); //q2s33vKz5sNPPQFzZygm4nqtjuPljaI+9q1mtcwRZ3U=
echo decrypt_string($msg);//your message

Question: How to get the last character of a string in PHP?

echo substr("web tehnology", -1); // y

Question: How to store array in constants??

define ("FRUITS", serialize($arrayData));
print_r(unserialize (FRUITS));

Question: What is the difference between bindParam and bindValue?
bindParam the variable is bound as a reference and will only be evaluated at the time that PDOStatement::execute() is called. PDOStatement::bindValue() is not work in this way.

Question: What is use of PHP_EOL?
PHP_EOL is used to find the newline character in a cross-platform-compatible way so it handles DOS/Mac/Unix issues.

Question: How to get accurate Ip Address of client Machine?

function ip_address(){
        if (array_key_exists($key, $_SERVER) === true){
            foreach (explode(',', $_SERVER[$key]) as $ip){
                $ip = trim($ip); // just to be safe

                if (filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false){
                    return $ip;
echo ip_address();//

Question: How to get extension of file??

$path ='/web-tech/myimage.png';
print_r(pathinfo($path, PATHINFO_EXTENSION));

Question: How to Check if PHP session has already started?

if(session_id() == '') {
    echo "session not started";
 echo "session started";

Question: NOW() equivalent function in PHP?

echo date("Y-m-d H:i:s"); //2015-11-14 9:52:32

Question: How to get all php functions?