Re: [PHP] Newbie question about isset and binary conditionals
That's a big help Mike. My server has the error level set such that my incorrect use of if($var) did not show undefined variables. Though everything seemed to work OK. I'm going my code and using if( TRUE or FALSE) isset() and empty() as appropriate. Al.. Mike Ford wrote: On 07 June 2004 14:04, Al wrote: I posted this previously; but the subject was misleading. You seem to have several possible misconceptions in your posting -- this may just be me misreading you, but anyway... I could use one additional clarification regarding good practice. As I understand the php manual the following is acceptable and I assume good practice. $foo= TRUE; Not only acceptable but encouraged. if($foo) do.. ; where $foo is a binary; but not a variable. $foo is always a variable -- it can contain values of several types, one of which is Boolean (not binary -- that's just a way of representing integers) TRUE/FALSE. isset should be used for variables, such as; isset($var) for variables and be careful with $var= ' '; etc. because $var is assigned, i.e., "set". To work out which test you need to use, it's crucial to understand what evaluates to FALSE in a Boolean context (which the test of an if() statement is. This is covered in precise detail in the PHP manual at http://www.php.net/manual/en/language.types.boolean.php#language.types.boole an.casting, but to summarize: the following are considered FALSE: Boolean FALSE, numeric zero (0 or 0.0), the strings "" and "0", an empty array or object, and NULL; all other values are TRUE. In addition to this, an unset variable will be evaluated as NULL, and hence considered FALSE, but PHP will also issue an undefined variable warning in this case (which may or may not be suppressed by your PHP configuration!). On the other hand, isset($var) will return TRUE if $var has been set to any value except NULL, and FALSE otherwise -- so an isset() test on all the other values listed above (including FALSE!) will be TRUE. Other tests you may want to look into are empty() http://www.php.net/empty and is_null() http://www.php.net/is-null; there are also some handy tables at http://uk.php.net/manual/en/types.comparisons.php to help you see what the various tests return. Cheers! Mike - Mike Ford, Electronic Information Services Adviser, Learning Support Services, Learning & Information Services, JG125, James Graham Building, Leeds Metropolitan University, Headingley Campus, LEEDS, LS6 3QS, United Kingdom Email: [EMAIL PROTECTED] Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
RE: [PHP] Newbie question about isset and binary conditionals
On 07 June 2004 14:04, Al wrote: > I posted this previously; but the subject was misleading. You seem to have several possible misconceptions in your posting -- this may just be me misreading you, but anyway... > I could use one additional clarification regarding good practice. > > As I understand the php manual the following is acceptable > and I assume > good practice. > > $foo= TRUE; Not only acceptable but encouraged. > > if($foo) do.. ; where $foo is a binary; but not > a variable. $foo is always a variable -- it can contain values of several types, one of which is Boolean (not binary -- that's just a way of representing integers) TRUE/FALSE. > isset should be used for variables, such as; > > isset($var) for variables and be careful with $var= ' '; > etc. because > $var is assigned, i.e., "set". To work out which test you need to use, it's crucial to understand what evaluates to FALSE in a Boolean context (which the test of an if() statement is. This is covered in precise detail in the PHP manual at http://www.php.net/manual/en/language.types.boolean.php#language.types.boole an.casting, but to summarize: the following are considered FALSE: Boolean FALSE, numeric zero (0 or 0.0), the strings "" and "0", an empty array or object, and NULL; all other values are TRUE. In addition to this, an unset variable will be evaluated as NULL, and hence considered FALSE, but PHP will also issue an undefined variable warning in this case (which may or may not be suppressed by your PHP configuration!). On the other hand, isset($var) will return TRUE if $var has been set to any value except NULL, and FALSE otherwise -- so an isset() test on all the other values listed above (including FALSE!) will be TRUE. Other tests you may want to look into are empty() http://www.php.net/empty and is_null() http://www.php.net/is-null; there are also some handy tables at http://uk.php.net/manual/en/types.comparisons.php to help you see what the various tests return. Cheers! Mike - Mike Ford, Electronic Information Services Adviser, Learning Support Services, Learning & Information Services, JG125, James Graham Building, Leeds Metropolitan University, Headingley Campus, LEEDS, LS6 3QS, United Kingdom Email: [EMAIL PROTECTED] Tel: +44 113 283 2600 extn 4730 Fax: +44 113 283 3211 -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Newbie question about isset and binary conditionals
I posted this previously; but the subject was misleading. I could use one additional clarification regarding good practice. As I understand the php manual the following is acceptable and I assume good practice. $foo= TRUE; if($foo) do.. ; where $foo is a binary; but not a variable. isset should be used for variables, such as; isset($var) for variables and be careful with $var= ' '; etc. because $var is assigned, i.e., "set". -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
[PHP] Newbie question about isset and binary conditionals
I posted this previously; but the subject was misleading. I could use one additional clarification regarding good practice. As I understand the php manual the following is acceptable and I assume good practice. $foo= TRUE; if($foo) do.. ; where $foo is a binary; but not a variable. isset should be used for variables, such as; isset($var) for variables and be careful with $var= ' '; etc. because $var is assigned, i.e., "set". -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
