PHP基础之数组

 'one', 2 => 'two', 3 => 'three' );
unset( $a[2] );
/* 将产生一个数组，定义为
   $a = array( 1=>'one', 3=>'three');
   而不是
   $a = array( 1 => 'one', 2 => 'three');
*/
$b = array_values($a);
// Now b is array(1 => 'one', 2 =>'three')
?>  

＜?php
$foo[bar] = 'enemy';
echo $foo[bar];
// etc
?＞

＜?php
error_reporting(E_ALL);
ini_set('display_errors', true);
ini_set('html_errors', false);
// Simple array:
$array = array(1, 2);
$count = count($array);
for ($i = 0; $i < $count; $i++) {
   echo "\nChecking $i: \n";
   echo "Bad: " . $array['$i'] . "\n";
   echo "Good: " . $array[$i] . "\n";
   echo "Bad: {$array['$i']}\n";
   echo "Good: {$array[$i]}\n";
}
?＞

Checking 0:
Notice: Undefined index:  $i in /path/to/script.html on line 9
Bad:
Good: 1
Notice: Undefined index:  $i in /path/to/script.html on line 11
Bad:
Good: 1

Checking 1:
Notice: Undefined index:  $i in /path/to/script.html on line 9
Bad:
Good: 2
Notice: Undefined index:  $i in /path/to/script.html on line 11
Bad:
Good: 2

 'apple', 'veggie' => 'carrot');

// 正确
print $arr['fruit'];  // apple
print $arr['veggie']; // carrot

// 不正确。This works but also throws a PHP error of
// level E_NOTICE because of an undefined constant named fruit
//
// Notice: Use of undefined constant fruit - assumed 'fruit' in...
print $arr[fruit];    // apple

// Let's define a constant to demonstrate what's going on.  We
// will assign value 'veggie' to a constant named fruit.
define('fruit','veggie');

// Notice the difference now
print $arr['fruit'];  // apple
print $arr[fruit];    // carrot

// The following is okay as it's inside a string.  Constants are not
// looked for within strings so no E_NOTICE error here
print "Hello $arr[fruit]";      // Hello apple

// With one exception, braces surrounding arrays within strings
// allows constants to be looked for
print "Hello {$arr[fruit]}";    // Hello carrot
print "Hello {$arr['fruit']}";  // Hello apple

// This will not work, results in a parse error such as:
// Parse error: parse error, expecting T_STRING' or T_VARIABLE' or T_NUM_STRING'
// This of course applies to using autoglobals in strings as well
print "Hello $arr['fruit']";
print "Hello $_GET['foo']";

// Concatenation is another option
print "Hello " . $arr['fruit']; // Hello apple
?> 

＜?php
echo $arr[somefunc($bar)];
?＞

＜?php
$error_descriptions[E_ERROR]  = "A fatal error has occured";
$error_descriptions[E_WARNING] = "PHP issued a warning";
$error_descriptions[E_NOTICE]  = "This is just an informal notice";
?＞

＜?php
$error_descriptions[1] = "A fatal error has occured";
$error_descriptions[2] = "PHP issued a warning";
$error_descriptions[8] = "This is just an informal notice";
?＞ 

 'red',
           'taste' => 'sweet',
           'shape' => 'round',
           'name'  => 'apple',
                       4        // key will be 0
         );

// is completely equivalent with
$a['color'] = 'red';
$a['taste'] = 'sweet';
$a['shape'] = 'round';
$a['name']  = 'apple';
$a[]        = 4;        // key will be 0

$b[] = 'a';
$b[] = 'b';
$b[] = 'c';
// will result in the array array(0 => 'a' , 1 => 'b' , 2 => 'c'),
// or simply array('a', 'b', 'c')
?> 

 4,
             'OS'        => 'Linux',
             'lang'      => 'english',
             'short_tags' => true
           );

// strictly numerical keys
$array = array( 7,
               8,
               0,
               156,
               -10
             );
// this is the same as array(0 => 7, 1 => 8, ...)

$switching = array(        10, // key = 0
                   5    =>  6,
                   3    =>  7,
                   'a'  =>  4,
                           11, // key = 6 (maximum of integer-indices was 5)
                   '8'  =>  2, // key = 8 (integer!)
                   '02' => 77, // key = '02'
                   0    => 12  // the value 10 will be overwritten by 12
                 );
// empty array
$empty = array();
?> 

＜?php
$colors = array('red', 'blue', 'green', 'yellow');

foreach ($colors as $color) {
   echo "Do you like $color?\n";
}

/* output:
Do you like red?
Do you like blue?
Do you like green?
Do you like yellow?
*/
?＞

 $color) {
   // won't work:
   //$color = strtoupper($color);

   //works:
   $colors[$key] = strtoupper($color);
}
print_r($colors);

/* output:
Array
(
   [0] => RED
   [1] => BLUE
   [2] => GREEN
   [3] => YELLOW
)
*/
?>

 'January', 'February', 'March');
print_r($firstquarter);
/* output:
Array
(
   [1] => 'January'
   [2] => 'February'
   [3] => 'March'
)
*/
?>