{"id":1371,"date":"2018-01-19T19:22:45","date_gmt":"2018-01-19T19:22:45","guid":{"rendered":"http:\/\/goofy-trucks.flywheelsites.com\/php-and-classes-page-2\/"},"modified":"2018-01-19T19:24:44","modified_gmt":"2018-01-19T19:24:44","slug":"php-and-classes-page-2","status":"publish","type":"post","link":"https:\/\/phpbuilder.com\/php-and-classes-page-2\/","title":{"rendered":"PHP and Classes Page 2"},"content":{"rendered":"
\n
\n
By Rod Kreisler<\/div>\n
on July 30, 2000<\/div>\n<\/p><\/div>\n
\n
\nWhen you create a function within a class with the same name as the
\nclass that function will execute whenever you create an object of that
\nclass. This is called a ‘constructor.’ It allows me to have default
\nvalues for each attribute automatically whenever I create an object:<\/div>\n
\n
\n<?php\u00a0$Basic\u00a0<\/span>=\u00a0new\u00a0<\/span>Style<\/span>;\u00a0<\/span>?><\/span>
\n<\/span>
\n<\/code><\/font><\/div>\n
\nYou define an instance of a class by giving it a name ($Basic) and
\nassigning it “=new ClassName;”.<\/div>\n
\nYou could also send different values for the variables as arguments when
\ndeclaring the new Style, but if you declare a value you have to declare
\nall of them that occur to the right of the one you declare (class
\nfunctions work just like regular functions in this respect). Meaning if
\nyou set ‘text’ to something different than the default given in Style,
\nthen you have to declare all the variables. There is an easier way. We
\ncan create a function that changes a single variable within the class:<\/div>\n
\n
\n<?php<\/p>\n

<\/span>Function\u00a0<\/span>Set<\/span>(<\/span>$varname<\/span>,<\/span>$value<\/span>)\u00a0{<\/p>\n

\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span>$this<\/span>-><\/span>$varname<\/span>=<\/span>$value<\/span>;<\/p>\n

}<\/p>\n

<\/span>?>
\n
<\/span>
\n<\/span>
\n<\/code><\/font><\/div>\n

\nSo to change the value of particular variable of an instance we can:<\/div>\n
\n
\n<?php\u00a0$Basic<\/span>-><\/span>Set<\/span>(<\/span>'size'<\/span>,<\/span>'2'<\/span>);\u00a0<\/span>?><\/span>
\n<\/span>
\n<\/code><\/font><\/div>\n
\nYou use the “->” operator to refer to a variable or a function of an
\ninstance. So the above tells the interpreter “Run function ‘Set()’ of
\ninstance ‘$Basic’.” It knows that “$Basic” is an instance of class
\n“Styles” because we declared it so. Similarly we can refer to variables
\nof an instance in the same manner (e.g. $Basic->text).<\/div>\n
\nLet’s create a Style for table headers that has some slightly different
\nattributes.<\/div>\n
\n<\/p>\n

<?php<\/p>\n

$Theader<\/span>=\u00a0new\u00a0<\/span>Style<\/span>;
\n
<\/span>$Theader<\/span>-><\/span>Set<\/span>(<\/span>'text'<\/span>,<\/span>'#0000FF'<\/span>);
\n
<\/span>$Theader<\/span>-><\/span>Set<\/span>(<\/span>'bgcol'<\/span>,<\/span>'#000000'<\/span>);<\/p>\n

<\/span>?>
\n
<\/span>
\n<\/span>
\n<\/code><\/font><\/div>\n

\nThere, that’s good enough. Now my table header has blue text on a black
\nbackground. I want my table body to be a slightly lighter gray than my
\nmain page, black is good for text, but maybe I’ll make the text smaller:<\/div>\n
\n<\/p>\n

<?php<\/p>\n

$Tbody<\/span>=new\u00a0<\/span>Style<\/span>;
\n
<\/span>$Tbody<\/span>-><\/span>Set<\/span>(<\/span>'bgcol'<\/span>,<\/span>'#AAAAAA'<\/span>);
\n
<\/span>$Tbody<\/span>-><\/span>Set<\/span>(<\/span>'size'<\/span>,<\/span>2<\/span>);<\/p>\n

<\/span>?>
\n
<\/span>
\n<\/span>
\n<\/code><\/font><\/div>\n<\/div>\n

<\/p>\n

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The hardest concept I’ve tried to understand since beginning to use PHP was that of classes. I’d never used a database engine but learning to use<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-1371","post","type-post","status-publish","format-standard","hentry","category-tutorials"],"_links":{"self":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1371","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/comments?post=1371"}],"version-history":[{"count":1,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1371\/revisions"}],"predecessor-version":[{"id":3246,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/posts\/1371\/revisions\/3246"}],"wp:attachment":[{"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/media?parent=1371"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/categories?post=1371"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/phpbuilder.com\/wp-json\/wp\/v2\/tags?post=1371"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}