PHP Language Summary

This is a summary of the PHP language.

Some nice things i found about PHP:

* No need to purchase additional ActiveX controls for email, gif manipulation, pdf handling, etc. Batteries included.
* Runs well on both IIS and Apache, Windows and Linux. Cross-platform power.
* Good performance. PHP is faster than VBScript and JScript, based on the Bagley benchmarks.
* Even if you are a VB programmer, provided you have some Javascript experience, you are already half-way up the learning curve, as PHP looks like Javascript with $ signs in front of variables.
* For those of you who miss ADO (i did), there’s ADOdb, a database abstraction library that works like ADO. And ASP2PHP is an automated VB to PHP converter.
* I recommend this PHP installer for IIS (ok, ok, I admit wrote it). The default PHP installer at php.net is not tuned for high performance IIS usage - this one is.

Feature	PHP
Example (print 1 to 10 on a web page)	for ($i=1; $i<=10; $i++) print “$i ”; ?>
Script Tags	If short tags are enabled in PHP.ini: If ASP tags are enabled in PHP.ini: <% %><%= return expression %>
End of statement	semicolon (;) is compulsory
Comments	// PHP comment 1 /* This is a multi-line Comment */ # PHP comment 3
Variables	Prefixed by $
Need to declare variables?	No, and every variable is preinitialised to type NULL, which is equivalent to false, the empty string and 0.$AVAR = 123;
Loosely Typed Variables	Yes. This means that the type of a variable can be changed at run-time. To change variable type, use typecasting or settype( )
Case-Sensitivity	Yes for variables, no for function-names and reserved words
Strings	Delimited by single-quotes, double-quotes or PERL heredoc style. $avar = 'this is a string'; $avar = "this is a string"; $avar = <<
String Concatenation	The . (dot) symbol.$s = ‘A’ . ‘B’;
String Evaluation	Yes, variables embedded in strings are evaluated if string delimited by double-quotes.$a = “A”; $b = “$a B”; /* now $b == ‘A B’ */
Common string constants	Line feed: “\n” Carriage return: “\r”Note that single-quoted ‘n’ is not converted to a line-feed for PHP. Only double-quoted strings are evaluated.
HTML encoding functions	htmlspecialchars($str) Converts < > & and ” to their HTML entity equivalents, eg. <>urlencode( ) All punctuation, accented characters, and any other non-ASCII characters are replaced with %xx encoding. Spaces converted to +.urldecode( )All punctuation, accented characters, and any other non-ASCII characters are replaced with %xx encoding. Spaces converted to +.
Regular Expressions	Built-in.if (preg_match (”/php/i”, $str)) print (”php found”);
Dates	$adate = time(); $adate=mktime(0,0,0,1,30,2000);print date('d-m-Y',$adate);
Arrays	Declare with $avar = array(1,’two’);For indexing use [ ]. Arrays begin with zero element.Use sizeof(array) function to get size of array.Arrays can be iterated over using: $val = reset($arr); $max = sizeof($arr); for ($i=0; $i<$max; $i++) { print "$val "; $val = next($arr); }/* or more simply */ foreach ($arr as $element) print "$element ";
Associative Arrays	Yes $avar = array(); $avar['newton']='isaac'; echo $avar['newton']; Note: You can append new elements to arrays with $avar[] = ’string to add’;
True and False	Has constants true and false.The following also evaluate to false: 0 /* zero */ "" /* empty string */ "0" /* string with zero */
Equality	== true if equal != not equal=== true if equal & same type !== not identical Note that some functions can return 0 or false (false is typically used to indicate failure) depending on the context. For these functions, you will need to use === to determine whether 0 or false was returned. Some problematic functions: strpos, strrpos, strstr, stristr, strrchr
Assignment statements	Allows C style shortcut assignments. For example, to append a string to a variable:$avar .= ‘append to end’;
Sending HTML to Browser	print $avar; echo “The avar variable ‘$avar’ is a string”;
If statements	if (strlen($avar) == 0) { $avar = "abc"; } else $avar .= 'end';
While statements	while ($a > 0) {$a -= 1;}
For loops	for ($i=0,$m=9; $i<$m; $i++){ print $i; }
Switch/Case	switch($aColor) { case 'red': do1;break; case 'green': do2;break; default: do3; break; }