Better way to check variable for null or empty string

Question

Since PHP is a dynamic language what s the best way of checking to see if a provided field is empty     I want to ensure that    null is considered an empty string a white space only string is considered empty that  0  is not considered empty   This is what I ve got so far    question   trim   POST  question      if           question            Handle error here     There must be a simpler way of doing this

User · Accepted Answer

Function for basic field validation  present and neither empty nor only white space function IsNullOrEmptyString  str       return   isset  str     trim  str

User · Answer

There is no better way but since it s an operation you usually do quite often  you d better automatize the process   Most frameworks offer a way to make arguments parsing an easy task  You can build you own object for that  Quick and dirty example    class Request           This is the spirit but you may want to make that cleaner  -      function get  key   default null   from null                 if   from                 if  isset        from   key                     return sanitize       strtoupper  from    key       didn t test that but it should work          else              if isset   REQUEST  key                   return sanitize   REQUEST  key              return  default                basics  Enforce it with filters according to your needs     function sanitize  data                  return addslashes trim  data                  your rules here     function isEmptyString  data                return  trim  data         or  data     null               function exists  key          function setFlash  name   value                     request   new Request     question   request- gt get  question        post    print  request- gt isEmptyString  question     Symfony use that kind of sugar massively    But you are talking about more than that  with your     Handle error here    You are mixing 2 jobs   getting the data and processing it  This is not the same at all   There are other mechanisms you can use to validate data  Again  frameworks can show you best pratices   Create objects that represent the data of your form  then attach processses and fall back to it  It sounds far more work that hacking a quick PHP script  and it is the first time   but it s reusable  flexible  and much less error prone since form validation with usual PHP tends to quickly become spaguetti code

User · Answer

empty   used to work for this  but the behavior of empty   has changed several times  As always  the php docs are always the best source for exact behavior and the comments on those pages usually provide a good history of the changes over time  If you want to check for a lack of object properties  a very defensive method at the moment is   if  is object  theObject   amp  amp   count get object vars  theObject    gt  0

User · Answer

I ll humbly accept if I m wrong  but I tested on my own end and found that the following  works for testing both string 0     and NULL valued variables   if    question          Handle success here     Which could also be reversed to test for success as such   if     question          Handle error here

User · Answer

This one checks arrays and strings   function is set  val      if is array  val   return  empty  val      return strlen trim  val     true   false

User · Answer

Beware false negatives from the trim   function     it performs a cast-to-string before trimming  and thus will return e g   Array  if you pass it an empty array   That may not be an issue  depending on how you process your data  but with the code you supply  a field named question   could be supplied in the POST data and appear to be a non-empty string   Instead  I would suggest    question     POST  question     if   is string      question   trim  question             Handle error here       If  question was a string  it will have been trimmed by this point

User · Answer

Beware false negatives from the trim   function     it performs a cast-to-string before trimming  and thus will return e g   Array  if you pass it an empty array   That may not be an issue  depending on how you process your data  but with the code you supply  a field named question   could be supplied in the POST data and appear to be a non-empty string   Instead  I would suggest    question     POST  question     if   is string      question   trim  question             Handle error here       If  question was a string  it will have been trimmed by this point

User · Answer

When you want to check if a value is provided for a field  that field may be a string   an array  or undifined   So  the following is enough  function isSet  param        return  is array  param   amp  amp  count  param      trim  param

User · Answer

Beware false negatives from the trim   function     it performs a cast-to-string before trimming  and thus will return e g   Array  if you pass it an empty array   That may not be an issue  depending on how you process your data  but with the code you supply  a field named question   could be supplied in the POST data and appear to be a non-empty string   Instead  I would suggest    question     POST  question     if   is string      question   trim  question             Handle error here       If  question was a string  it will have been trimmed by this point

User · Answer

There is no better way but since it s an operation you usually do quite often  you d better automatize the process   Most frameworks offer a way to make arguments parsing an easy task  You can build you own object for that  Quick and dirty example    class Request           This is the spirit but you may want to make that cleaner  -      function get  key   default null   from null                 if   from                 if  isset        from   key                     return sanitize       strtoupper  from    key       didn t test that but it should work          else              if isset   REQUEST  key                   return sanitize   REQUEST  key              return  default                basics  Enforce it with filters according to your needs     function sanitize  data                  return addslashes trim  data                  your rules here     function isEmptyString  data                return  trim  data         or  data     null               function exists  key          function setFlash  name   value                     request   new Request     question   request- gt get  question        post    print  request- gt isEmptyString  question     Symfony use that kind of sugar massively    But you are talking about more than that  with your     Handle error here    You are mixing 2 jobs   getting the data and processing it  This is not the same at all   There are other mechanisms you can use to validate data  Again  frameworks can show you best pratices   Create objects that represent the data of your form  then attach processses and fall back to it  It sounds far more work that hacking a quick PHP script  and it is the first time   but it s reusable  flexible  and much less error prone since form validation with usual PHP tends to quickly become spaguetti code

User · Answer

There is no better way but since it s an operation you usually do quite often  you d better automatize the process   Most frameworks offer a way to make arguments parsing an easy task  You can build you own object for that  Quick and dirty example    class Request           This is the spirit but you may want to make that cleaner  -      function get  key   default null   from null                 if   from                 if  isset        from   key                     return sanitize       strtoupper  from    key       didn t test that but it should work          else              if isset   REQUEST  key                   return sanitize   REQUEST  key              return  default                basics  Enforce it with filters according to your needs     function sanitize  data                  return addslashes trim  data                  your rules here     function isEmptyString  data                return  trim  data         or  data     null               function exists  key          function setFlash  name   value                     request   new Request     question   request- gt get  question        post    print  request- gt isEmptyString  question     Symfony use that kind of sugar massively    But you are talking about more than that  with your     Handle error here    You are mixing 2 jobs   getting the data and processing it  This is not the same at all   There are other mechanisms you can use to validate data  Again  frameworks can show you best pratices   Create objects that represent the data of your form  then attach processses and fall back to it  It sounds far more work that hacking a quick PHP script  and it is the first time   but it s reusable  flexible  and much less error prone since form validation with usual PHP tends to quickly become spaguetti code

User · Answer

Use PHP s empty   function  The following things are considered to be empty      an empty string  0  0 as an integer  0 0  0 as a float   0   0 as a string  NULL FALSE array    an empty array   var   a variable declared  but without a value    For more details check empty function

User · Answer

empty   used to work for this  but the behavior of empty   has changed several times  As always  the php docs are always the best source for exact behavior and the comments on those pages usually provide a good history of the changes over time  If you want to check for a lack of object properties  a very defensive method at the moment is   if  is object  theObject   amp  amp   count get object vars  theObject    gt  0

User · Answer

Beware false negatives from the trim   function     it performs a cast-to-string before trimming  and thus will return e g   Array  if you pass it an empty array   That may not be an issue  depending on how you process your data  but with the code you supply  a field named question   could be supplied in the POST data and appear to be a non-empty string   Instead  I would suggest    question     POST  question     if   is string      question   trim  question             Handle error here       If  question was a string  it will have been trimmed by this point

User · Answer

to be more robust  tabulation  return      I define   function is not empty string  str        if  is string  str   amp  amp  trim  str     t n r 0                   return true      else         return false        code to test  values   array false  true  null   abc    23   23   23 5   23 5            0   0   foreach   values as  value        var export  value       if  is not empty string  value            print   is a none empty string  n        else         print   is not a string or is an empty string n        sources      https   www php net manual en function is-string php   https   www php net manual en function trim php

User · Answer

to be more robust  tabulation  return      I define   function is not empty string  str        if  is string  str   amp  amp  trim  str     t n r 0                   return true      else         return false        code to test  values   array false  true  null   abc    23   23   23 5   23 5            0   0   foreach   values as  value        var export  value       if  is not empty string  value            print   is a none empty string  n        else         print   is not a string or is an empty string n        sources      https   www php net manual en function is-string php   https   www php net manual en function trim php

User · Answer

Use PHP s empty   function  The following things are considered to be empty      an empty string  0  0 as an integer  0 0  0 as a float   0   0 as a string  NULL FALSE array    an empty array   var   a variable declared  but without a value    For more details check empty function

User · Answer

This one checks arrays and strings   function is set  val      if is array  val   return  empty  val      return strlen trim  val     true   false

User · Answer

There is no better way but since it s an operation you usually do quite often  you d better automatize the process   Most frameworks offer a way to make arguments parsing an easy task  You can build you own object for that  Quick and dirty example    class Request           This is the spirit but you may want to make that cleaner  -      function get  key   default null   from null                 if   from                 if  isset        from   key                     return sanitize       strtoupper  from    key       didn t test that but it should work          else              if isset   REQUEST  key                   return sanitize   REQUEST  key              return  default                basics  Enforce it with filters according to your needs     function sanitize  data                  return addslashes trim  data                  your rules here     function isEmptyString  data                return  trim  data         or  data     null               function exists  key          function setFlash  name   value                     request   new Request     question   request- gt get  question        post    print  request- gt isEmptyString  question     Symfony use that kind of sugar massively    But you are talking about more than that  with your     Handle error here    You are mixing 2 jobs   getting the data and processing it  This is not the same at all   There are other mechanisms you can use to validate data  Again  frameworks can show you best pratices   Create objects that represent the data of your form  then attach processses and fall back to it  It sounds far more work that hacking a quick PHP script  and it is the first time   but it s reusable  flexible  and much less error prone since form validation with usual PHP tends to quickly become spaguetti code

User · Answer

When you want to check if a value is provided for a field  that field may be a string   an array  or undifined   So  the following is enough  function isSet  param        return  is array  param   amp  amp  count  param      trim  param

User · Answer

Old post but someone might need it as I did     if  strlen  str     0   do what ever     replace  str with your variable  NULL and    both return 0 when using strlen

User · Answer

I ll humbly accept if I m wrong  but I tested on my own end and found that the following  works for testing both string 0     and NULL valued variables   if    question          Handle success here     Which could also be reversed to test for success as such   if     question          Handle error here

User · Answer

Old post but someone might need it as I did     if  strlen  str     0   do what ever     replace  str with your variable  NULL and    both return 0 when using strlen

[php] Better way to check variable for null or empty string?

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