Testing for one of a list of values.

For 2023 (and 2024 ...) - we are now fully retired from IT training.
We have made many, many friends over 25 years of teaching about Python, Tcl, Perl, PHP, Lua, Java, C and C++ - and MySQL, Linux and Solaris/SunOS too. Our training notes are now very much out of date, but due to upward compatability most of our examples remain operational and even relevant ad you are welcome to make us if them "as seen" and at your own risk.

Lisa and I (Graham) now live in what was our training centre in Melksham - happy to meet with former delegates here - but do check ahead before coming round. We are far from inactive - rather, enjoying the times that we are retired but still healthy enough in mind and body to be active!

I am also active in many other area and still look after a lot of web sites - you can find an index ((here))

Question [PHP] When you have a string of conditions in an 'if' clause and one side of the conditional expression is the same in each condition, is there any shortcut to avoid writing out every expression in full. For examples, rather than writing
if(($name!='Lisa')&&($name!='Leah')&&($name!='Christine')) {
can I write
if($name!=('Lisa'||'Leah'||'Christine')) {

Answer The short answer is "no - you must write it all out if you're using the != operator". In Perl 6 (different language) you WILL have a shortened syntax for this sort of thing but that's highly unusual. But lets' take a wider look at other alternatives.

In php you could write
if (!ereg ('^(Lisa|Leah|Christine)$,$name)) { ....
although that would be slighly less efficient at run time.

I do worry about hardcoding data such as people's names into a program. When Lisa decides she now wants to be called by a different name, or when Chloe joins the team, you're back to the code! Your code would be more maintainable if you had an array of names in a separate file. You could compromise with something like:

$people = array("Hermione","Bob","Sally");

if (in_array($name,$people)) { ...

Note - if you're reading your data into $name from a MySQL database, the INoperator used in a WHERE clause will allow you to filter your data before it ever reaches your PHP variables.

(written 2007-05-22, updated 2010-05-15)

Associated topics are indexed as below, or enter http://melksh.am/nnnn for individual articles

H106 - PHP - Arrays
  [409] Functions and commands with dangerous names - (2005-08-11)
  [603] PHP - setting sort order with an associative array - (2006-02-13)
  [773] Breaking bread - (2006-06-22)
  [832] Displaying data at 5 items per line on a web page - (2006-08-14)
  [1116] PHP adding arrays / summing arrays - (2007-03-23)
  [1451] More PHP sample and demonstration programs - (2007-12-01)
  [1614] When an array is not an array - (2008-04-17)
  [2215] If nothing, make it nothing. - (2009-06-02)
  [2274] PHP preg functions - examples and comparision - (2009-07-08)
  [2915] Looking up a value by key - associative arrays / Hashes / Dictionaries - (2010-08-11)
  [2920] Sorting - naturally, or into a different order - (2010-08-14)
  [3004] Increment operators for counting - Perl, PHP, C and others - (2010-10-18)
  [3379] Sorting data the way YOU want it sorted - (2011-08-05)
  [3534] Learning to program in PHP - Regular Expression and Associative Array examples - (2011-12-01)
  [4068] Arrays in PHP - contain different and even mixed data types - (2013-04-24)
  [4072] Splitting the difference with PHP - (2013-04-27)
  [4244] Disambiguation - PHP List - (2014-03-07)

H104 - PHP - Control Statements
  [340] Code and code maintainance efficiency - (2005-06-08)
  [353] Wimbledon Neck - (2005-06-20)
  [406] Assignment, equality and identity in PHP - (2005-08-08)
  [421] Don't repeat code - use loops or functions - (2005-08-21)
  [657] The ternary operator in Python - (2006-03-25)
  [863] Double and Triple equals operator in PHP - (2006-09-12)
  [962] Breaking a loop - Ruby and other languages - (2006-12-03)
  [1191] Smart English Output - via PHP and Perl ? : operator - (2007-05-18)
  [1220] for loop - how it works (Perl, PHP, Java, C, etc) - (2007-06-06)
  [1477] Decisions - small ones, or big ones? - (2007-12-18)
  [1696] Saying NOT in Perl, PHP, Python, Lua ... - (2008-07-04)
  [1825] Question Mark - Colon operator (Perl and PHP) - (2008-10-08)
  [2304] Extracting real data from an exported file in PHP or Perl - (2009-07-25)
  [2912] Predictions for the seagull population - (2010-08-09)
  [3200] How a for loop works Java, Perl and other languages - (2011-03-12)
  [3397] Does a for loop evaluate its end condition once, or on every iteration? - (2011-08-18)
  [3895] Flowchart to program - learning to program with Well House - (2012-10-14)
  [3914] While, for, foreach or something else to loop. - (2012-11-06)
  [4322] Learning to Program - the conditional statement (if) - (2014-11-21)
  [4323] Learning to program - Loop statements such as while - (2014-11-22)

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Some other Articles

A Fresh horse
Returning multiple values from a function (Perl, PHP, Python)
No switch in Python
Training information - England, Scotland, Wales and Ireland
Testing for one of a list of values.
From Web to Web 2
Back off home with our best wishes
The last tree to leaf
Regular Express Primer
Drawing hands on a clock face - PHP

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This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

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