exchange the values in two variables without using additional variables for storage?

To swap $a and $b:

list($a,$b) = array($b,$a);

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access the values passed to a function?how

Use the names from the function prototype:

function commercial_sponsorship($letter, $number) { 
    print "This episode of Sesame Street is brought to you by ";
    print "the letter $letter and number $number.\n";
}

commercial_sponsorship('G', 3);
commercial_sponsorship($another_letter, $another_number);

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how associate multiple elements with a single key?

Store the multiple elements in an array:

$fruits = array('red' => array('strawberry','apple'),
                'yellow' => array('banana'));

Or, use an object:

while ($obj = mysql_fetch_object($r)) {
    $fruits[ ] = $obj;
}

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How to check whether two floating-point numbers are equal?

Use a small delta value, and check if the numbers are equal within that delta:

$delta = 0.00001;

$a = 1.00000001;
$b = 1.00000000;

if (abs($a - $b) < $delta) { /* $a and $b are equal */ }

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You want to extract part of a string, starting at a particular place in the string

Use substr( ) to select your substrings:

$substring = substr($string,$start,$length);
$username = substr($_REQUEST['username'],0,8);

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Php get_meta_tags-Extracts all meta tag content attributes

get_meta_tags — Extracts all meta tag content attributes from a file and returns an array

<?php// Assuming the above tags are at www.example.com$tags = get_meta_tags('http://www.example.com/');
// Notice how the keys are all lowercase now, and
// how . was replaced by _ in the key.echo $tags['author'];       // nameecho $tags['keywords'];     // php documentationecho $tags['description'];  // a php manualecho $tags['geo_position']; // 49.33;-86.59?>

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PHP Redirect - Redirect Script?

PHP Redirect Function

header('Location:  destination.php');
exit();

ou need the Location: part so the browser knows what header it's 

receiving. Also, don't forget to 

do an exit() or die() right after the redirect. 

 

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Control Structures

• if
• else
• elseif/else if
• Alternative syntax for control structures
• while
• do-while
• for
• foreach
• break
• continue
• switch
• declare
• return
• require
• include
• require_ once
• include_ once
• goto

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Finding the Position of a Value in an Array

Use array_search( ) . It returns the key of the found value. If the value is not in the array, it returns false:

$position = array_search($value, $array);
if ($position !== false) {
    // the element in position 

//$position has $value as its 

//value in array $array
}

Use in_array( ) to find if an array contains a value; use array_search( ) to discover where that value is located. However, because array_search( ) gracefully handles searches in which the value isn't found, it's better to use array_search( ) instead of in_array( ). The speed difference is minute, and the extra information is potentially useful:

$favorite_foods = array(1 => 'artichokes', 'bread', 'cauliflower', 'deviled eggs');
 $food = 'cauliflower'; $position = array_search($food, $favorite_foods);
 if ($position !== false)
{
echo "My #$position favorite food is $food";
}
 else {
 echo "Blech! I hate $food!";
 }

Use the !== check against false because if your string is found in the array at position 0, the if evaluates to a logical false, which isn't what is meant or wanted.

If a value is in the array multiple times, array_search( ) is only guaranteed to return one of the instances, not the first instance.

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Turning an Array into a String

convert it into a  formatted string.

Use join( ):

// make a comma delimited list
$string = join(',', $array);

Or loop yourself:

$string = '';

foreach ($array as $key => $value) {
    $string .= ",$value";
}

$string = substr($string, 1); // remove leading ","

If you can use join( ), do; it's faster than any PHP-based loop. However, join( ) isn't very flexible. First, it places a delimiter only between elements, not around them. To wrap elements inside HTML bold tags and separate them with commas, do this:

$left = '<b>'; $right = '</b>'; $html = $left . join("$right,$left", $html) . $right;

Second, join( ) doesn't allow you to discriminate against values. If you want to include a subset of entries, you need to loop yourself:

$string = ''; foreach ($fields as $key => $value) { // don't include password if ('password' != $key) { $string .= ",<b>$value</b>"; } } $string = substr($string, 1); // remove leading ","

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