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.

// file.txt contains the sentence: Hello World!
$filename = 'file.txt';
$file = fopen($filename, 'r');
$string = fread( $file, filesize($filename) );
var_dump($string);
// file.txt now contains at the end: Hello World!

You’ll notice that this is the same tip as fread() and doesn’t belong. It should be considered ‘removed’.

pg. 162

preg_match_all: 157-158

pg. 161

array_combine: 73
array_key_exists: 79-80

function strtotimefix($val,$timestamp=0){
	if ($timestamp==0){ $timestamp = time(); }
	if (date('m') == date('m',strtotime('-1 month'))){
		$timestamp = strtotime('-3 days',$timestamp);
	}else{
		$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 kindle version of PHP Reference: Beginner to Intermediate PHP5 is available for $8.99 through Amazon.com, at just over half the price of the main book!

• 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, and spaces are allowed:
(123) 456.7890

^((\(\d{3}\)\s?|\d{3}\.)|(\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})?)$

A kindle version of PHP Reference: Beginner to Intermediate PHP5 is available for $3.99 through Amazon, the lowest priced general PHP book available!

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To date, there have also been 97 revenue generating print copies of the paperback sold and 60 digital Kindle editions sold. The majority of sales are through Amazon.com, generating a lot less income per book than copies sold through lulu.com.

• Total Revenue (all sources): $501.18
• Costs to create the book: ~$600
  (computer monitor, ISBN, review copies, office space rent, etc.)
• Hours spent writing: 175

In other words, with costs included, I’ve lost ~$100 creating the book. If that was not factored in, the hourly wage for creating the book so far would be $2.86/hour (in reality it is $0.00).

With over 8,000 downloads which are and will always remain free in PDF form, a donation of $1 for each download would have changed it to ~$33/hour. Would you consider purchasing a paperback PHP book copy today or donating to my hosting costs when downloading a free PDF of the PHP reference book? Thanks!