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PHP Arrays and Control Structures

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While Listing Array Values

3:50 with Alena Holligan

Arrays are a collection of items, which mean that, often times, we want to do the same thing with each item in the array. Loops allow us to do just that. We can loop through an entire array, or part of an array, and perform any number of actions on each item. In this video we'll use our while loop to loop through the todo list.

Documentation

PLEASE NOTE: This function has been DEPRECATED as of PHP 7.2.0. Relying on this function is highly discouraged. However, you may still encounter the each function both in PHP and other languages, so knowing how it works is still important.

each: returns the current key and value pair from an array and advance the array cursor.

list: assigns variables as if they were an array.

Additional Examples

//increment before evaluating the $count variable
$count=0;
while ((list($key, $val) = each($todo)) && (++$count <= 2)) {
    echo "$key => $val\n";
}

//increment after evaluating the $count variable
$count=1;
while ((list($key, $val) = each($todo)) && ($count++ <= 2)) {
    echo "$key => $val\n";
}

The above examples will both return the second and third elements (array keys 1 and 2).

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    Arrays are collection of items, which means that 0:00
    often times we want to do the same thing with each item in the array. 0:03
    Loops allow us to do just that. 0:08
    We can loop through an entire array, or part of an array, and 0:10
    perform any number of actions on each item. 0:15
    Let's go into work spaces and 0:18
    see how we can use a while loop to loop through each item on our learning list. 0:19
    Let's comment out this loop for years. 0:25
    Now let's open our indexed arrays file. 0:34
    We'll copy the code from our learned list along with the asort. 0:36
    Now we're ready to loop through each item. 0:44
    Let's pull up the documentation for the each function in PHP. 0:47
    PHP each function. 0:52
    We see that we pass it the array and it returns the current key and 0:56
    value pair from that array. 1:00
    And then it advances the array cursor. 1:03
    If we scroll down to example 2, We see 1:06
    that each is typically used in conjunction with list to traverse an array. 1:11
    If we look at list, we see that it's not really a function. 1:17
    But a language construct used to assign a list of variables in one operation. 1:23
    Let's go back to the example in the documentation for 1:30
    the Each function, And let's copy this while loop. 1:33
    Back in workspaces, we can paste in the loop and change our array. 1:41
    Now let's run the script in our console. 1:47
    PHP loops.php. 1:51
    We see our list sorted by value. 1:54
    We can also combine this with our count to only return a certain number of items, 1:57
    let's say 2. 2:03
    We'll add a variable named $count, we'll set it equal to 0. 2:05
    And then we can add a condition to our loop, 2:11
    && $count++ < 2. 2:17
    In the last video, 2:21
    we added our incrementing operator to the beginning of the variable. 2:22
    So that the number was incremented before the comparison was made. 2:26
    This time I want to compare first and then increment. 2:31
    So I add the incrementing operator to the end of the variable. 2:35
    This way the first time 0 will be evaluated as less than 2. 2:39
    And the second time, 1 will be evaluated as less than 2. 2:44
    Now let's run the script again. 2:49
    Now we see two empty items. 2:53
    Hey wait what went wrong? 2:55
    Remember when I talked about priority. 2:57
    The double ampersand has a higher priority than equal. 3:00
    So it's as if we put parentheses around the each and the count. 3:04
    That's not what we want to happen. 3:11
    So we have two options. 3:13
    We can change the double ampersand to the keyword AND or 3:15
    we can put parentheses around the first evaluation. 3:20
    I want to keep with the consistency of using double ampersands. 3:24
    So I'm going to put parentheses around this first evaluation. 3:29
    Now when I run the script, we see the first two items on the list. 3:41
    This could be a good way to see a couple items on your list 3:45
    without getting overwhelmed. 3:48

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