Common functions and keywords in the basic part of PHP

 bool setcookie ( string $name [, string $value [, int $expire = 0 [, string $path [, string $domain [, bool $secure = false [, bool $httponly = false ]]]] ]] )
 explain:This requires that you place calls to this function prior to any output, including  and  tags as well as any whitespace.
 example:setcookie("TestCookie", $value, time ()+3600);


 bool define ( string $name , mixed $value [, bool $case_insensitive = false ] ) //Define a constant
 const CONSTANT = 'Hello World'; //Use the practical keyword const to define a constant Constant, the effect is the same

 example:define("CONSTANT", "Hello world.");

 bool defined ( string $name ) //Check whether a constant exists


 bool isset ( mixed $var [, mixed $ ... ] ) //Check if a variable exists

 void unset ( mixed $var [, mixed $... ] ) // Release a variable


 bool function_exists ( string $function_name ) // Check if a function Exists


 string get_class ([ object $obj ] ) //Get the class name of an object

 array get_object_vars ( object $obj ) // Return an associative array composed of object attributes

 bool file_exists ( string $filename ) // Check if the file or directory exists



 Comparison operator
 $a == $b equals, if $a equals $b after type conversion.
 $a === $b is congruent if $a is equal to $b and their types are also the same.
 $a != $b is not equal, if $a is not equal to $b after type conversion.
 $a <> $b is not equal, if $a is not equal to $b after type conversion.
 $a !== $b is not congruent if $a is not equal to $b, or their types are different.
 $a < $b is less than $b, if $a is strictly less than $b.
 $a > $b is greater than, if $a is strictly greater than $b.
 $a <= $b is less than or equal to, if $a is less than or equal to $b.
 $a >= $b is greater than or equal to $a if $a is greater than or equal to $b.


 PHP supports an error control operator: @. When placed before a PHP expression, any error message that expression may produce is ignored.

 Execution operator, backtick operator is invalid when safe mode is activated or shell_exec() is turned off.
  $output = `ls -al`;
 echo "$output";
 ?>

 There are two string operators . The first is the concatenation operator ("."), which returns the concatenated string of its left and right arguments. The second is the concatenation assignment operator (".="), which appends the right argument to the left argument.

 Array operator

 $a + $b Union Union of $a and $b.
 $a == $b is equal TRUE if $a and $b have the same key/value pair.
 $a === $b is congruent TRUE if $a and $b have the same key/value pairs and are of the same order and type.
 $a != $b is not equal TRUE if $a is not equal to $b.
 $a <> $b is not equal TRUE if $a is not equal to $b.
 $a !== $b is not equal. TRUE if $a is not equal to $b.


 The type operator instanceof is used to determine whether a PHP variable belongs to an instance of a certain class:
  class MyClass{}
 class NotMyClass{}
 $a = new MyClass;
 var_dump($a instanceof MyClass);
 var_dump($a instanceof NotMyClass);
 ?>
 The above routine will output:
 bool(true)
 bool(false)


 bool is_a ( object $object , string $class_name [, bool $ allow_string = FALSE ] ) //Return TRUE if the object belongs to this class or this class is the parent class of this object



 foreach loop array or object
 foreach (array_expression as $value)
 statement
 foreach (array_expression as $key => $value)
 statement


 require and include are almost exactly the same, except for the way failure is handled. require generates an E_COMPILE_ERROR level error when an error occurs. In other words, it will cause the script to abort and include will only generate a warning (E_WARNING), and the script will continue to run.
 include 'vars.php';

 The require_once statement is exactly the same as the require statement. The only difference is that PHP will check whether the file has already been included, and if so, it will not include it again.

 goto: (compared to C language, it is a castrated product)
 The goto operator can be used to jump to another location in the program.The target position can be marked with the target name followed by a colon, and the jump instruction is the goto followed by the mark of the target position.
 goto in PHP has certain limitations. The target location can only be in the same file and scope, which means that it cannot jump out of a function or class method, nor can it jump into another function. It also cannot jump into any loop or switch structure.
 You can break out of a loop or switch. The usual usage is to use goto instead of multiple levels of break.
  goto a;
 echo 'Foo';
 a:
 echo 'Bar';
 ?>
 The above routine will output:
 Bar

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