Arrays

array_intersect
array_merge
array_pop
array_push
array_reverse
array_walk
count
in_array

Date and Time

date
mktime
strtotime
time

Filesystem

clearstatcache
copy
fclose
fgets
file
filemtime
filesize
file_exists
fopen
fread
fwrite
is_dir
is_file
readfile

Headers

header
headers_sent
setcookie

Mail

mail

Numbers

ceil
floor
number_format
round

Miscellaneous

define
eval
exit

Network

fsockopen

PHP Options

ini_get
ini_restore
ini_set
phpinfo

 

Execution

exec

REGULAR EXPRESSION SYNTAX
^	Start of string
$	End of string
.	Any single character
(a|b)	a or b
(...)	Group section
[abc]	Item in range (a or b or c)
[^abc]	Not in range (not a or b or c)
\s	White space
a?	Zero or one of a
a*	Zero or more of a
a+	One or more of a
a{3}	Exactly 3 of a
a{3,}	3 or more of a
a{3,6}	Between 3 and 6 of a
\	Escape character
[:punct:]	Any punctuation symbol
[:space:]	Any space character
[:blank:]	Space or tab

PCRE MODIFIERS
i	Case-insensitive
s	Period matches newline
m	^ and $ match lines
U	Ungreedy matching
e	Evaluate replacement
x	Pattern over several lines

FUNCTION ARGUMENT ORDER

array_push ( array, element )

in_array ( needle, haystack )

explode ( separator, string )

split ( pattern, string )

preg_split ( pattern, string )

ereg ( pattern, string )

strpos ( haystack, needle )

str_replace ( search, replace, string )

fopen() MODES
r	Read
r+	Read and write, prepend
w	Write, truncate
w+	Read and write, truncate
a	Write, append
a+	Read and write, append

DATE FORMATTING
Y	4 digit year	2005
y	2 digit year	05
F	Long month	January
M	Short month	Jan
m	Month (leading zeros)	01 to 12
n	Month	1 to 12
D	Short day name	Mon
l	Long day name	Monday
d	Day (leading zeros)	01 to 31
j	Day	1 to 31
h	12 Hour (leading zeros)	01 to 12
g	12 Hour	1 to 12
H	24 Hour (leading zeros)	00 to 23
G	24 Hour	0 to 23
i	Minutes (leading zeros)	00 to 59
s	Seconds (leading zeros)	00 to 59
w	Day of week 1	0 to 6
z	Day of year	0 to 365
W	Week of year 2	1 to 53
t	Days in month	28 to 31
a		am or pm
A		AM or PM
B	Swatch Internet Time	000 to 999
S	Ordinal Suffix	st, nd, td, th
T	Timezone of machine	GMT
Z	Timezone offset (seconds)
O	Difference to GMT (hours)	+0200
I	Daylight savings	1 or 0
L	Leap year	1 or 0
U	Seconds since Epoch
c	ISO 8601 (PHP 5)
r	RFC 2822
1.	date("w"): 0 is Sunday, 6 is Saturday.
2.	Week that overlaps two years belongs to year that contains most days of that week. Hence week number for 1st January of a given year can return 53rd week if week belongs to previous year. date("W", mktime(0, 0, 0, 12, 28, $year)) always gives correct number of weeks in $year.
3.	The Epoch was the 1st January 1970.

Regex

ereg
eregi
ereg_replace
eregi_replace
split
spliti
preg_match
preg_match_all
preg_replace
preg_split

Sessions

session_destroy
session_id
session_start

Strings

addslashes
crypt
echo
explode
implode
md5
nl2br
sprintf
strip_tags
stripslashes
stristr
strpos
strrev
strstr
strtolower
strtoupper
str_replace
substr
trim

URLs

rawurldecode
rawurlencode
urldecode
urlencode

Variables

empty
is_array
is_int
is_null
is_numeric
is_object
isset
serialize
unserialize

SuperGlobals

$_ENV
$_GET
$_POST
$_COOKIE
$_SESSION
$_SERVER
$_FILES
$_REQUEST
$GLOBALS