Siemens SIMATIC S7-1500 Function Manual page 128

Using String or Character tags in expressions
On your HTML page, you use an expression in which the character string for reading a tag is
enclosed in quotation marks, for example in forms.
Possible HTML code used:
<input type="text" name="appfield" value="myvalue">
If you read the displayed value for the "value" attribute from a PLC tag in this expression, the
HTML code appears as follows:
<input type="text" name="appfield" value=":="Varname".MyString:">
By reading the PLC tag, the Web server outputs the value 'ABC'. In HTML, the code is then
represented as follows:
<input type="text" name="appfield" value=" 'ABC' ">
If you have used single quotes instead of double quotes in your HTML code to enclose the
attributes, the web server passes on the content of the tag enclosed in two single quotes to
the browser. As a result of this, the browser does not output the content of the String or
Character tag, since two consecutive single quotation marks each form a closed sequence.
The values to be read are located between these sequences and are not output by the
browser.
In this context, note in particular that the character string with double quotation marks is not
identical to two single quotation marks even if they appear to be identical.
Note
The code is not adapted automatically during an update to firmware as of V1.6.
Adapt your HTML code if you have used single quotation marks to enclose attributes for the
"Read PLC tags" function.
Figure 3-70
Web server
Function Manual, 11/2019, A5E03484625-AG
Example of HTML code with attribute in single quotation marks
Web pages
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