|--column1--|--column2--|
|     0     |    1234   |
|     3     |    5678   |
-------------------------

A MySQL query took a while, but didn’t time out when the list of WHERE column2=’value’ was less than 7000, but it was just overwhelmed at 10,000. Okay, fine, time to go to phase two: in_array().
There was an existing array of values for column2, so I could simply pull a list of <3 from MySQL (quick) and then loop through (foreach) each of the results and check whether they are in_array() for the original source. If they were, just save them to a brand new array that I’ll use to work further through the problem. For clarification, that means that the system should go through 10,000+ iterations and check if each value is in_array(). If you had not already guessed, this was disastrous. In_Array() is very inefficient, and if you are dealing with an array that is more than 100 or so values, you’ll quickly learn this fact. So what to do? Use isset().
Isset(), as a function, is incredibly fast. It only checks whether something exists, and is a great way to check for whether something exists in an array. However, the trick is using isset() will look at the KEYS, while in_array() will look at the VALUES. Is that problem? Not if you build the original array as [value]=>value (set the KEY and VALUE the same). Now, as long as your values are valid keys and unique, this won’t be a problem. Then, you can use a foreach loop to check whether it is found in the original array. Here is some sample code:

$array_source = array('abc'=>'abc','def'=>'def','ghi'=>'ghi');
$array_results = array('xyz','ghi');
foreach ($array_results as $v){
  if (isset($array_source[$v])){ //fast
    $result[] = $v; //if found, save it to a fresh array
  }
}

What was the final result? The query, run 6 different times for 6 different data sets, went from a total execution time exceeding 2 minutes (MySQL), to not working at all (in_array), to 0.18 seconds. Yes, less than one second! That is the power for checking whether a value is set when comparing arrays. Isset() is even faster by a notable amount when compared to array_diff().

UPDATE table SET column1=’newvalue’,column2=’nextvalue’ WHERE column3=’value’

It is still a work in progress, but the new PHP Code Checker will not execute your code, simply scan it as a string and run a battery of tests to find these mistakes. It is only a few weeks and less than 10 hours of work in it so far, but it is already at version 0.2 and is ready to help you. There is more coming soon, so keep tabs on the site and I hope it helps you deal with those tough code problems!

Photo courtesy of Zach Klein

I could attempt to explain this, but someone has already done a very good job of this, so I’d rather just provide a link to their content. The post is from the author of “High Performance MySQL”, Baron Schwartz, and covers writing an SQL Exclusion Join. The key area of interest is the section on LEFT OUTER joins. He offers this example query:

SELECT apples.Variety
FROM apples
    LEFT OUTER JOIN oranges
        ON apples.Price = oranges.Price
WHERE oranges.Price IS NULL

When in doubt, find someone smarter to answer the question for you. Thanks Baron!

function preprint($arr){
  echo '< pre>'.print_r($arr).'< /pre>';
}
$array = scandir(getcwd());
preprint($array); // nicely formatted display of the array

 
Of course, you can skip the print/echo portion if you don’t wish to display the contents and just use the array to perform other checks, but you get the idea.

function strtotimefix($val,$timestamp=0){
	if ($timestamp==0){ $timestamp = time(); }
	if (date('m') == date('m',strtotime('-1 month'))){
		$timestamp = strtotime('-3 days',$timestamp);
	}else{
		if($timestamp==0){$timestamp = time();}
	}
	$strtotime = strtotime($val,$timestamp);
	return $strtotime;
}

So what’s happening? Basically, the function will check if the numeric month is the same between the current month and the month through ‘-1 month’. If so, it subtracts 3 days from the current timestamp, then runs through the strtotime function using the new timestamp. If everything is fine, nothing is altered, so you don’t have to worry that using the strtotimefix() function will break a perfectly normal strtotime(‘-1 month’) call. Be advised that if you are not doing a call with ‘-x month’, the function will return an incorrect timestamp by 3 days (I hope to update it to be self-aware and only ‘fix’ when the bug would be introduced).

Updated on March 30, 2010:
Changed it to -3 days to deal with February/March.

• A copy of the PHP book with a tab on pages 149 and 150 for common RegEx syntax
• A link to RegExPal, a color coding Regular Expression tester.

Common Regular Expressions:

Date and Time RegEx

Time format (no seconds):
HH:MM am/pm

^([1-9]|1[012]):(0[0-9]|[1-5][0-9])\s?(am|AM|pm|PM)$

Date in mm/dd/yyyy format, with an option for m/d/yyyy (exclude zero’s)

^(0?[1-9]|1[012])[ \/.-](0?[1-9]|[12][0-9]|3[01])[ \/.-](19|20)\d\d$

Date in dd/mm/yyyy format, with an option for d/m/yyyy (exclude zero’s)

^(0?[1-9]|[12][0-9]|3[01])[ \/.-](0?[1-9]|1[012])[ \/.-](19|20)\d\d$

Demographics RegEx

Age in years – max 122

^([0-9]|[1-9][0-9]|[1-9][0-1][0-9]|[1-9]2[0-2])$

Height in Feet and Inches:
6’3″

^([1-8]')?\s?([1-9]|1[01])$

Contact Information RegEx

U.S. Phone Number – parenthesis, periods, dashes, underscore, and spaces are allowed:
(123)456-7890
(123) 456 – 7890
( 123 )456-7890
1234567890
123.456.7890
123-456-7890
123 456 7890

^[\(\s\._-]*\d{3}[\)\s\._-]*\d{3}[\s\._-]*\d{4}$

U.S. Zip Code – 5 or 9 digit with dash

^\d{5}([\-]\d{4}){0,1}$

Email Address – (use preg_match) credit goes to fightingforalostcause.net

/^[-_a-z0-9\'+*$^&%=~!?{}]++(?:\.[-_a-z0-9\'+*$^&%=~!?{}]+)*+@(?:(?![-.])[-a-z0-9.]+(?<![-.])\.[a-z]{2,6}|\d{1,3}(?:\.\d{1,3}){3})(?::\d++)?$/iD

Currency RegEx

Currency – U.S. Dollars and Cents with commas for multiple’s of 1000 and a period for the decimal:
$12,000.23

^\$?([1-9]{1}[0-9]{0,2}(\,[0-9]{3})*(\.[0-9]{0,2})?|[1-9]{1}[0-9]{0,} (\.[0-9]{0,2})?|0(\.[0-9]{0,2})?|(\.[0-9]{1,2})?)$

Currency – British Pounds with commas for multiple’s of 1000 and a period for the decimal:
£12,000.23

^\u00A3?([1-9]{1}[0-9]{0,2}(\,[0-9]{3})*(\.[0-9]{0,2})?|[1-9]{1}[0-9]{0,} (\.[0-9]{0,2})?|0(\.[0-9]{0,2})?|(\.[0-9]{1,2})?)$

Currency – Euros with periods for multiple’s of 1000 and a comma for the decimal:
€12.000,23

^\u20AC?([1-9]{1}[0-9]{0,2}(\.[0-9]{3})*(\,[0-9]{0,2})?|[1-9]{1}[0-9]{0,} (\,[0-9]{0,2})?|0(\,[0-9]{0,2})?|(\,[0-9]{1,2})?)$

Currency – Euros, French style, with spaces for multiple’s of 1000 and a comma for the decimal:
€12 000,23

^\u20AC?([1-9]{1}[0-9]{0,2}(\s[0-9]{3})*(\,[0-9]{0,2})?|[1-9]{1}[0-9]{0,} (\,[0-9]{0,2})?|0(\,[0-9]{0,2})?|(\,[0-9]{1,2})?)$

Here is a quick screenshot of some of the highlighting in action:

Be advised that this is based on JavaScript regular expressions, which are comparable to the PERL compatible RegEx functions, such as preg_replace() and preg_match(). It’s a good idea to get familiar with this syntax, as ereg() and eregi() style functions will be removed from PHP6 when it is released, sometime in the future. Make sure to also checkout the Regular Expressions Cookbook contributed to by the author of RegExPal.com.

This tip is courtesy of a great article, 10 Advanced PHP Tips Revisited

When referencing an array’s value via a numeric key, you follow the variable name ($variable) with the numeric index, enclosed by square brackets [5]. e.g. $variable[5] = ‘value’
However, when $variable represents a string, using the same syntax will return a string with the character at the position specified by the numeric index (0 marks the first character in the $variable string). An example:

$string = 'abcdefg';
var_dump($string[2]);

Output: string(1) “c”

Where this comes into play is when using isset() rather than strlen(). Consider the following example:

$string = 'abcdefg';
if (isset($string[5])){
  echo $string[5].' found!';
}

Output: f found!

$string = 'abcdefg';
if (isset($string[7])){
     echo $string[7].' found!';
  }else{
     echo 'No character found at position 7!';
}

Output: No character found at position 7!

This is faster than using strlen() because, “… calling a function is more expensive than using a language construct.” It’s little tricks like this that will keep your code lean and efficient. Thanks to Chris Shiflett and Sean Coates for their contributions to the referenced article.

https://phpreferencebook.com/?variable=value&name=Mario%20Lurig&gender=male%21

or

https://phpreferencebook.com/?variable=value&name=Mario Lurig&gender=male!

1. Display the whole string (everything after the question mark)

• <?php echo $_SERVER['QUERY_STRING']; ?>

• variable=value&name=Mario%20Lurig&gender=male

2. Display the whole string decoded (convert %## to original characters)

• <?php echo urldecode($_SERVER['QUERY_STRING']); ?>

• variable=value&name=Mario Lurig&gender=male!

3. Show each variable and value as an array (already decoded)

• <?php print_r($_GET); ?>

• Array ( [variable] => value [name] => Mario Lurig [gender] => male!

• <?php echo '<pre>'; print_r($_GET); echo '< /pre>'; ?>

• Array
  (
      [variable] => value
      [name] => Mario Lurig
      [gender] => male!
  )
  

There are lots of options from there, so don’t let this be the end of your exploration of how to display a query string value on a page. If you have any great tricks, feel free to share them in the comments below!