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Breaded IT » Web Development » Internet Tools » PHP Notes 101
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Variables
Loosely typed, no declarations necessary
Preceded by $, must start with a letter, followed by any alphanumeric and '_' combination
Assigning a value:
$Pi = 3.14;
Variable Scope
No such thing as a global variable.
Variables only exist inside their function.
Variables from the calling function are not available in the called function but they are avaialble via the special array GLOBALS
ie. $GLOBALS("Pi") = 3.14
Indirect references to variables
$position = "David"
$$position = "Technician"
print $David
outputs "Technician"
Variable tests/management:
isset($position) returns true if $position has been set and is other than NULL
also:
isset($arr["offset"])
isset($obj->property)
unset($position) removes & frees up from memory $position
empty($position) opposite of isset()
Superglobals
$_GET[] // All get vars received from client browser
$_POST[] // All post vars received from client browser
$_COOKIE[] // All cookiess received from client browser
$_ENV[] // Env vars
$_SERVER[] // Web server vars
Available everywhere
Datatypes
Integers
Floating Point
Strings (can be really big)
$Position = 'Technician'
$Position = "Technician"
Double quotes allows variables embedded in the string construct to automatically be replaced by the variable contents
Special sequences:
\n | Newline |
\t | Tab |
\" | Double quote |
\\ | Backslash |
\0 | Ascii 0 (Null) |
\r | Line feed |
\$ | Escapes $ sign so is not treated as a variable name |
\x{hex #} | Hex number ie \0x32 |
String offsets
$Position = "Technician"
Print $Position{2} // prints 'c'
Booleans
Data type | False | True |
Integer | 0 | not 0 |
Floating point | 0.0 | not 0.0 |
String | Empty or zero (0) | Neither empty or zero |
NULL | Always | Never |
Array | 0 elements | 1 or more elements |
Object | Never | Always |
Resource | Never | Always |