PHP Arrays
for
Fun and Profit

UPHPU Meeting

November 17, 2005

Mac Newbold

mac@macnewbold.com

Who am I?

• Full-time self-employed computer geek

  • Code Greene (www.codegreene.com, partner)

  • Wide variety of PHP/MySQL web sites and applications

  • Fan of FreeBSD, Firefox, Flyspray, etc.

• Background: B.S. C.S. ’01, M.S. C.S. ’05

  • University of Utah – Go Utes!

The Plan

• Array Basics

  • Lists and Associative Arrays

  • Array operators and functions

• Using Arrays

  • Looping with Arrays

  • Sorting Arrays

  • Using arrays as parameters to functions

• Data Structures with Arrays

The Array Data Type in PHP

• www.php.net/manual/en/- language.types.array.php

• Two types: Lists and Associative Arrays

  • Every array is pairs of keys and values

• Consecutive numeric keys (0-based) is a list

  • Implied when you don’t specify any keys

• Other keys (i.e. strings) is an associative array, a.k.a. hash, map, etc.

Making Arrays

• $list = array(‘foo’,$bar,”BAZ”,1,2,3);

  • List: [0]=>’foo’, [1]=>$bar, [2]=>… … …

  • echo $list[0]; à foo

• $map=array(“dog”=>”brown”,”cat”=>”fat”)

  • Associative array: [dog]=>brown, [cat]=>fat

  • echo $map[“dog”]; à brown

• $list[] = 4;

• $map[“mouse”] = ”quiet”;

Array Operators

• 5 for comparison, 1 other

• ==, !=, <> – Test for [in]equality

  • Same key/value pairs (using “type juggling”)

• ===, !== – Test for identity

  • Same pairs, same order, same types

• Union: + (see also array_merge())

  • Numeric keys get reindexed

  • For duplicate keys, left hand dominates

Array Functions

• Over 75 array functions

• Some are obvious and self-explanatory:

  • array(), is_array(), unset(), in_array(), count(), shuffle(), array_keys(), array_values(), array_reverse(), array_sum(), array_product()

• array_[push,pop,shift,unshift]()

  • Push and pop at the end

  • Shift (on) or unshift (off) at the beginning

Array Functions 2

• Set operations: Union, Diff, Intersect

• array_[u]{diff,intersect}[_[u]{assoc,key}]()

  • Plain: compare values

  • Key: compare keys

  • Assoc: compare values and keys

  • u/uassoc/ukey: Compare with callback function

  • udiff/uintersect: allow recursive/deep compare

• Rarely need anything but plain, key, assoc

Array Functions 3

• $str = implode(“:”,$arr);

• $arr = explode(“:”,$str);

• $arr = array_combine($keys,$values);

• $arr = array_flip($arr); // val=>key

• $arr = array_pad($arr_in, 10, “”);

• array_slice, array_splice – cut/paste

• Extract, compact – array <=> variables

Array Functions 4

• Array_walk() – apply callback to pairs

• Array_map() – return array of results of applying callback to pairs

• Array_unique() – delete duplicate values

• Array_rand() – choose random key(s)

• list($first,$second,$third) = $arr;

• There are a bunch more too…

The Plan

• Array Basics

  • Lists and Associative Arrays

  • Array operators and functions

• Using Arrays

  • Looping with Arrays

  • Sorting Arrays

  • Using arrays as parameters to functions

• Data Structures with Arrays

Looping with Arrays

• Arrays have internal pointers for iterating

  • Current(), prev(), next(), reset(), end(), key()

  • list($key,$val) = each($arr) – grabs next pair

• foreach ($arr as $v) { }

• foreach ($arr as $k => $v) { }

• while (list($k,$v) = each($arr)) { }

• for ($i=0; $i<count($arr); $i++) { $arr[$i];}

Sorting Arrays

• sort() – sort by value

• ksort() – sort by key

• asort() – sort by value, keep associations

• rsort(), krsort(), arsort() – reverse

• usort(), uksort(), uasort() – custom compare

• natsort(), natcasesort() – “natural order”

• shuffle() – You guessed it…

Arrays as Parameters

• Many string functions can do more complex things when arrays are used as parameters:

  • $arr = array(‘foo’,’bar’);

  • str_replace($arr,”baz”,$str);

  • str_replace($arr,array(‘blah’,’boo’),$str);

• Passing arrays by reference lets you “return” multiple values from a function:

  • function getUser(&$result) { }

Arrays as Return Values

• Rather than returning by reference, you can simply return an array directly:

  • return array(“rv1”=>17,”rv2”=>42);

• Many standard functions return arrays:

  • MySQL for example: mysql_fetch_*()

  • Assoc gets associative, row gets numeric, array gets either, or both at once

• Remember: list($rv1, $rv2) = getPair();

Data Structures with Arrays

• Plain arrays already do a whole lot:

  • List, vector, hash, map, set, stack, queue, etc.

• Trees and recursive structures are easy:

  • Multi-dimensional arrays: $arr[3][7][9];

  • Hash/map of arrays - $arr[“person1”][“name”]

• “Struct” (a la C) or “mock object”

  • $obj = array(“name”=>”joe”, “age”=>”64”);

  • Quicker/simpler than going fully OOP

Arrays and HTTP/HTML

• Make arrays with GET or POST variables:

  • index.php?list[0]=foo&list[1]=bar

  • index.php?list[]=blah&list[]=hm&list[]=wow

• HTML Forms for arrays:

  • <input name=“person[name]”>

  • <input type=“checkbox” name=“list[yes]”>

  • <select multiple name=“choices[]”>

  • Always use [] for multiple select – the only way

Grand Finale

• Arrays are pretty simple, yet incredibly powerful at the same time. They’re well worth any time you invest in learning to use them well.

• Any questions?