Array Variables

• In PHP, array variables look just like scalar variables (different from Perl where arrays always start with an "at" symbol (@) and associative arrays (called hashes) start with a percent sign (%).
• Simple assignment to an array is done using the array() function. This creates an array with 12 items:

  $months = array( "Jan", "Feb", "Mar", "Apr", "May", "Jun", 
  		"Jul", "Aug", "Sep", "Oct", "Nov", "Dec" ) ;
  

• Note that the array items are numbered starting with 0 (zero), not 1 (one). So in this case, we have $months[0] (Jan) through $months[11] (Dec). $months[1] is "Feb", not "Jan".
• You may also assign values directly to an array element. If you do not specify the array index, the next available index is used. This creates an array with 7 elements:

  $days[0] = "Sunday" ;
  $days[1] = "Monday" ;
  $days[2] = "Tuesday" ;
  $days[3] = "Wednesday" ;
  $days[4] = "Thursday" ;
  $days[] = "Friday" ;
  $days[] = "Saturday" ;
  

• To reference individual array items, use the array name with the index. If you reference an array variable in a double quoted string, you need to surround the variable and index with curly braces.

  print 'Today is ' . $days[1] ;
  print "Tomorrow is {$days[2]}" ;
  print "Yesterday was {$days[$x-1]}" ;
  

• Performing an operation on each item in an array may be done in a few different ways:

  $languages = array( "C", "C++", "Perl", "PHP", "Visual Basic", "Java" ) ;
  
  // for loop
  for ( $i=0; $i < count($languages); $i++ ) {
  	print "Language: {$languages[$i]}\n" ;
  }
  
  // foreach loop
  foreach ( $languages as $item ) {
  	print "Language: $item\n" ;
  }
  

• Array indices don't need to be numbers. They may be any valid expression, including strings. Here we use names as array indices and phone extensions as values:

  $days = array( "Jan" => 31, "Feb" => 28, "Mar" => 31, "Apr" => 30, ... ) ;
  

• In this case, the foreach loop can retrieve both the key and the value for each item:

  foreach ( $days as $month => $number ) {
  	print "There are $number days in $month\n" ;
  }
  
  print 'January has ' . $days["Jan"] . " days.\n" ;