PHP Reference

<?php ?> → PHP opening and closing tags.

echo → Outputs text to the browser.

print → Outputs text (similar to echo).

; → Ends a PHP statement.

// comment → Single-line comment.

/* comment */ → Multi-line comment.

$x = 10; → Declares a variable.

$name = "John"; → String variable.

$isActive = true; → Boolean variable.

$arr = [1,2,3]; → Array variable.

$obj = new stdClass(); → Object variable.

string → Text.

int → Integer number.

float → Decimal number.

bool → true or false.

array → List of values.

object → Instance of a class.

null → No value.

= → Assignment.

+ - * / % → Math operators.

== → Equal (value).

=== → Identical (value and type).

!= / !== → Not equal.

> < >= <= → Comparisons.

&& → AND.

|| → OR.

! → NOT.

. → String concatenation.

if ($x > 5) {} → Runs if condition is true.

else {} → Runs if false.

elseif ($x == 5) {} → Another condition.

switch ($x) {} → Multiple case conditions.

for ($i=0; $i<10; $i++) {} → Repeats code fixed times.

while ($x < 10) {} → Runs while condition is true.

do {} while ($x < 10); → Runs once then repeats.

foreach ($arr as $value) {} → Loops array values.

foreach ($arr as $k => $v) {} → Loops keys and values.

function name() {} → Declares a function.

function sum($a,$b) { return $a+$b; } → Function with parameters.

return → Sends value back.

$arr = [1,2,3]; → Indexed array.

$arr["name"] = "John"; → Associative array.

count($arr) → Number of items.

array_push($arr,$x) → Add item.

array_pop($arr) → Remove last.

in_array($x,$arr) → Check value exists.

strlen($str) → String length.

strtolower($str) → Lowercase.

strtoupper($str) → Uppercase.

trim($str) → Remove spaces.

str_replace("a","b",$str) → Replace text.

$_GET → Data from URL query.

$_POST → Data from form POST.

$_REQUEST → GET + POST.

$_FILES → Uploaded files.

$_SERVER → Server info.

$_SESSION → Session data.

$_COOKIE → Cookies.

fopen("file.txt","r") → Open file.

fread($f,100) → Read file.

fwrite($f,"text") → Write file.

fclose($f) → Close file.

file_get_contents("file.txt") → Read whole file.

file_put_contents("file.txt",$data) → Write whole file.

include "file.php"; → Includes file (warning if missing).

require "file.php"; → Includes file (fatal error if missing).

include_once → Include once.

require_once → Require once.

session_start() → Starts session.

$_SESSION["user"]="John"; → Store session value.

session_destroy() → End session.

setcookie("name","John",time()+3600) → Create cookie.

$_COOKIE["name"] → Read cookie.

date("Y-m-d") → Current date.

time() → Current timestamp.

strtotime("next week") → Convert text to time.

mysqli_connect(host,user,pass,db) → Connect to MySQL.

mysqli_query($conn,$sql) → Run query.

mysqli_fetch_assoc($res) → Fetch row.

mysqli_num_rows($res) → Row count.

mysqli_close($conn) → Close connection.