Basic Syntax

Data Types
Operators and Expressions
Logical Operators
Comparison Operators
Including Files

PHP syntax is generally similar to C/C++ (mixed with a bit of Perl, Java). One important difference is that PHP is not case-sensitive (although variable names are).

Statements in PHP are separated by semicolons.
Variables in PHP are not "declared", rather they are created and typed when first used.
PHP variables begin with a $ sign (PERL like)
PHP has three comment types
1. // single line comments
2. /* ... */ multiline comments
3. # Single line comments

You can make PHP report errors when uninitialized variables are used by adjusting PHP's error reporting:

For example to print: Hello World

  <?php
  $hello = "Hello World";
  echo $hello;
  ?>

PHP also picks up many variables from the environment. For example, $_SERVER['PHP_SELF'] , gives the path portion of the URL of the current file: /tutorial/htmlguid/php/syntax.phtml.

Data Types

PHP data types include integer numbers, doubles, strings, and arrays of any of the above. They are declared and automatically typed when first used. Explicit types can be created using cast or settype functions. Examples

numbers

   $x = 10 //integer
   $y = 5.5 //float
   $z = (double) 10;

Strings

Strings can be defined using single quotes or double quotes. Variables within double quoted strings are expanded. e.g.

<php
  $hello = "Hello";
  $world = "World";
  $helloworld = "$hello $world";
  $whoops = '$hello $world';
  echo $helloworld, "<br>";
  echo $whoops;
?>

yields:

Hello World
$hello $world

Arrays

Arrays in PHP can be both normal arrays and associative arrays or hashes. For example:

    $a[0] = "First";
    $a[1] =  "Second";
              // we can add a third element without specifying an index
    $a[] = "Third";
    echo $a[0], $a[1], $a[2];

Giving:

First, Second, Third

PHP also supports associative arrays. These can be declared either by using the array function or explicitly as seen below:

   $assoc = array("Firstname" => "Robert",
          "Lastname" =>  "Rittenhouse");
     // alternatively
   $assoc ["Midname"] = "George";
   echo $assoc['Firstname'], " ", $assoc['Midname'], " ", $assoc['Lastname'];

Yielding: Robert George Rittenhouse

Operators and Expressions

example	name	result
$a + $b	Addition	Sum of $a and $b.
$a - $b	Subtraction	Remainder of $b subtracted from $a.
$a * $b	Multiplication	Product of $a and $b.
$a / $b	Division	Dividend of $a and $b.
$a % $b	Modulus	Remainder of $a divided by $b.
$s1 . $s2	String concatenation	$s2 = "Hello " . "World"; //$s2 is "Hello World"

Logical Operators

example	name	result
$a and $b	And	True of both $a and $b are true.
$a or $b	Or	True if either $a or $b is true.
$a xor $b	Xor	True if either $a or $b is true, but not both.
! $a	Not	True if $a is not true.
$a && $b	And	True if both $a and $b are true.
$a \|\| $b	Or	True if either $a or $b is true.

Comparison Operators

Comparison operators, as their name imply, allow you to compare two values.

example	name	result
$a == $b	Equal	True if $a is equal to $b.
$a != $b	Not equal	True if $a is not equal to $b.
$a < $b	Less than	True if $a is strictly less than $b.
$a > $b	Greater than	True if $a is strictly greater than $b.
$a <= $b	Less than or equal to	True if $a is less than or equal to $b.
$a >= $b	Greater than or equal to	True if $a is greater than or equal to $b.

Including Files

You can include files using the include or require commands. The files in the directory /web/html/fragments/ can be included without specifying a path. One useful file is a test for access from McMurry which you can use with the statement <?php require('ismcm.pinc'); ?>. This adds the function isMcMurry(). and can be used as:

<php
echo  $_SERVER['REMOTE_ADDR'] , " ";
if (isMcMurry() ){
    echo " At McMurry ";
} else {
    echo  " Not McMurry ";
}
?>

prints: 38.107.191.81 IS At McMurry

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