[PHP] Convert to half-width numbers and check if they are numbers

Sep 9, 2020 PHP for beginners

The function used this time is `` mb_convert_kana``

For example, suppose it is described as follows

$ age = 20; // ← half-width numbers

if (is_numeric ($ age)) {
  print ($ age.'Year');
} else {
  print ('* Age is not a number');
}

The display is as follows

20-year-old

With the function is_numeric You can check if the specified parameter is a number. In the above example, ($ age) is checked.

If $ age ='aiueo'

* Age is not a number

Will be displayed.

Also, if you set $ age = '20' (double-byte number) instead of $ age = '20', In the same way, “* Age is not a number” is displayed.

Even if the user has to enter in half-width characters as above, It is often the case that you accidentally enter full-width characters.

Therefore, even if you enter a full-width number, you can write it so that it will be converted to a half-width number.

As mentioned at the beginning, the function mb_convert_kana is used there. If you write the code first, it will be as follows.

$ age = 20; // ← full-width numbers

$ age = mb_convert_kana ($ age,'n','UTF-8');
if (is_numeric ($ age)) {
  print ($ age.'Year');
} else {
  print ('* Age is not a number');
}

Even though ** 20 ** is entered as a full-width number, it is displayed as follows.

20-year-old

Describes mb_convert_kana ** mb ** → Abbreviation for multibyte, a word used when dealing with full-width characters such as Japanese ** convert_kana ** → Function to convert various kana

Various conversions can be performed depending on the parameters, Here, it is possible to specify that it is converted to a half-width number by setting it to 'n'.

'UTF-8' specifies the character code used.

In the above code, ** 20 ** is a full-width number, but thanks to “**‘n’ **”, it is corrected to a half-width number. Therefore, it will be recognized as a numerical value and displayed as ** 20 years old **.

that’s all. Thank you for your hard work.