Managing & Using MySQL, 2nd Edition

A Short Language Primer

This section introduces the basic syntax of PHP. If you’re familiar with high-level languages such as C, Java, JavaScript, or Perl, you’ll be at home with PHP. The current version of PHP is PHP 4, and some details we present here are specific to this version.

As discussed previously, PHP scripts are surrounded by the PHP start tag <?php and the end tag ?>. You’ll often see the start tag abbreviated as <?, but this conflicts with the emerging XHTML standard and should be avoided.

Statements in a script are terminated with a semicolon. Statements can be formatted for readability by including any amount of whitespace—such as space characters, tab characters, or blank lines—in a script.

Comments can be included in a PHP script using the following styles:

// One line comment
  
#  Another one line comment
  
/* A
   multiple line
   comment */

Data can be output with the statements print , echo , and printf . The first two are often interchangeable, but echo has an advantage in that it can take more than one argument. The printf statement is used for more complex output and is identical to that used in other programming languages such as C and scripting languages such as awk. Consider a few examples:

// These are the same
echo "This is output";
print "This is output";
  
// echo can output more than one argument
echo 123, "is a number";
  
// printf can be used to control formatting
// This outputs 3.14
printf("pi is %.2f\n", 3.14159);

Variables are identified by the prefix ...